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Articles 181 - 210 of 228
Full-Text Articles in Aerospace Engineering
Kinematical Modelling And Its Analytical Inverse Kinematic Solution For The Handling Mechanism Of An Agricultural Robot, Sinem Gozde Defterli
Kinematical Modelling And Its Analytical Inverse Kinematic Solution For The Handling Mechanism Of An Agricultural Robot, Sinem Gozde Defterli
Electronic Theses and Dissertations
Early detection of the crop diseases helps to prevent failure in the amount and the quality of the production. In agricultural robotics, the idea of a disease detection robot is a fresh and an innovative hot-button topic. The exclusion of the diseased parts from the strawberry plants for further analyses is one of the main tasks of a recently developed strawberry robot. To this purpose, the handling mechanism in the robot needs to achieve an accurate manipulation task to reach the target. Reaching, cutting and storing the diseased leaf are challenging and delicate processes during the procedure of the handling …
The Impact Of Automation Reliability And Fatigue On Reliance, Ryan Wohleber
The Impact Of Automation Reliability And Fatigue On Reliance, Ryan Wohleber
Electronic Theses and Dissertations
The objective of this research is to inform the design of dynamic interfaces to optimize unmanned aerial vehicle (UAV) operator reliance on automation. A broad goal of the U.S. military is to improve the ratio of UAV operators to UAVs controlled. Accomplishing this goal requires the use of automation; however, the benefits of automation are jeopardized without appropriate operator reliance. To improve reliance on automation, this effort sought to accomplish several objectives organized into phases. The first phase aimed to validate metrics that could be used to gauge operator fatigue online, to understand how the reliability of automated systems influences …
Planar Laser Induced Fluorescence Experiments And Modeling Study Of Jets In Crossflow At Various Injection Angles, Luke Thompson
Planar Laser Induced Fluorescence Experiments And Modeling Study Of Jets In Crossflow At Various Injection Angles, Luke Thompson
Electronic Theses and Dissertations
Planar Laser Induced Fluorescence (PLIF) with acetone seeding was applied to measure the scalar fields of an axisymmetric freejet and an inclined jet-in-crossflow as applicable to film cooling. From the scalar fields, jet-mixing and trajectory characteristics were obtained. In order to validate the technique, the canonical example of a nonreacting freejet of Reynolds Numbers 900-9000 was investigated. Desired structural characteristics were observed and showed strong agreement with computational modeling. After validating the technique with the axisymmetric jet, the jet-in-crossflow was tested with various velocity ratios and jet injection angles. Results indicated the degree of wall separation for different injection angles …
Evaporative Vapor Deposition For Depositing 2d Materials, Kevin Gleason
Evaporative Vapor Deposition For Depositing 2d Materials, Kevin Gleason
Electronic Theses and Dissertations
The development of a new deposition technique called evaporative vapor deposition (EVD) is reported, allowing deposition and formation of atomically-thin, large area materials on arbitrary substrates. This work focuses on the highly popular monolayer material – graphene oxide (GO). A droplet of a GO solution is formed on a heated polymer substrate, and maintained at steady-state evaporation (all droplet parameters are held constant over time). The polymer substrate is laser patterned to control the droplet's contact line dynamics and the droplet's contact angle is maintained using a computer controlled syringe pump. A room temperature silicon wafer is translated through the …
Deposition Thickness Modeling And Parameter Identification For Spray Assisted Vacuum Filtration Process In Additive Manufacturing, August Mark
Electronic Theses and Dissertations
To enhance mechanical and/or electrical properties of composite materials used in additive manufacturing, nanoparticles are often time deposited to form nanocomposite layers. To customize the mechanical and/or electrical properties, the thickness of such nanocomposite layers must be precisely controlled. A thickness model of filter cakes created through a spray assisted vacuum filtration is presented in this paper, to enable the development of advanced thickness controllers. The mass transfer dynamics in the spray atomization and vacuum filtration are studied for the mass of solid particles and mass of water in differential areas, and then the thickness of a filter cake is …
Experimental And Numerical Investigations Of Microdroplet Evaporation With A Forced Pinned Contact Line, Kevin Gleason
Experimental And Numerical Investigations Of Microdroplet Evaporation With A Forced Pinned Contact Line, Kevin Gleason
HIM 1990-2015
Experimental and numerical investigations of water microdroplet evaporation on heated, laser patterned polymer substrates are reported. The study is focused on both (1) validating numerical models with experimental data, (2) identifying how changes in the contact line infuences evaporative heat transfer and (3) determining methods of controlling contact line dynamics during evaporation. Droplets are formed using a bottom-up methodology, where a computer-controlled syringe pump supplies water to a ~200[micro]m in diameter fluid channel within the heated substrate. This methodology facilitates precise control of the droplets growth rate, size, and inlet temperature. In addition to this microchannel supply line, the substrate …
The Thermodynamics Of Planetary Engineering On The Planet Mars, Christopher Barsoum
The Thermodynamics Of Planetary Engineering On The Planet Mars, Christopher Barsoum
HIM 1990-2015
Mars is a potentially habitable planet given the appropriate planetary engineering efforts. In order to create a habitable environment, the planet must be terraformed, creating quasi-Earth conditions. Benchmarks for minimum acceptable survivable human conditions were set by observing atmospheric pressures and temperatures here on Earth that humans are known to exist in. By observing a positive feedback reaction, it is shown how the sublimation of the volatile southern polar ice cap on Mars can increase global temperatures and pressures to the benchmarks set for minimum acceptable survivable human conditions. Given the degree of uncertainty, utilization of pressure scale heights and …
Load Transfer In An Isolated Particle Embedded Within An Epoxy Matrix, Erik Durnberg
Load Transfer In An Isolated Particle Embedded Within An Epoxy Matrix, Erik Durnberg
Electronic Theses and Dissertations
Particulate composites are widely used in many aerospace applications such as protective coatings, adhesives, or structural members of a body and their mechanical properties and behavior have gained increasing significance. The addition of modifiers such as alumina generally leads to improved mechanical properties. This addition also enables the non-invasive study of the load transfer between the particle and the matrix. Understanding the load transfer between the particulate and the matrix material is the first step to understanding the behavior and mechanical properties of the composite as a whole. In this work, samples with an isolated alumina particle embedded in an …
Ignition Studies Of Diisopropyl Ketone, A Second-Generation Biofuel, Owen Pryor
Ignition Studies Of Diisopropyl Ketone, A Second-Generation Biofuel, Owen Pryor
HIM 1990-2015
This thesis focuses on ignition of diisopropyl ketone (DIPK), a new biofuel candidate that is produced by endophytic conversion. The ignition delay times behind reflected shockwaves were modeled in a high-pressure shock tube. The ignition delay times were compared to other biofuels and gasoline surrogates. Parametric studies of the ignition delay experiments were performed between 1-10 atm and 900 -1200K. An OH optical sensor was developed in conjunction for the ignition delay experiments. The OH optical sensor uses a microwave discharge lamp to generate light at 308 nm that will then be shined through the combustion reaction. Using Beer-Lambert law …
Nondestructive Analysis Of Advanced Aerospace Materials Via Spectroscopy And Synchrotron Radiation, Albert Manero
Nondestructive Analysis Of Advanced Aerospace Materials Via Spectroscopy And Synchrotron Radiation, Albert Manero
Electronic Theses and Dissertations
Advanced aerospace materials require extensive testing and characterization to anticipate and ensure their integrity under hostile environments. Characterization methods utilizing synchrotron X-Ray diffraction and spectroscopy can decrease the time required to determine an emerging material's readiness for application through intrinsic information on the material response and failure mechanisms. In this study, thermal barrier coating samples applicable to turbine blades of jet engines were studied using Raman and Photoluminescence spectroscopy as well as Synchrotron X-ray diffraction while Kevlar based fiber composites applicable to ballistic resistant armor were studied using Raman spectroscopy to investigate the mechanical state and corresponding damage and failure …
Application Of Non-Local Approaches For Predicting The Response Of V-Notch Under Thermomechanical Fatigue Loading, Trung Nguyen
Application Of Non-Local Approaches For Predicting The Response Of V-Notch Under Thermomechanical Fatigue Loading, Trung Nguyen
HIM 1990-2015
The topic of this thesis is the construction of a formula to approximate stress-strain responses at notches under thermomechanical fatigue (TMF) loading. The understanding of material behavior of the V-notched component which experiences TMF is important to the mechanical industries where V-notched structures are often utilized. In such applications, it is crucial that the designers be able to predict the material behavior; therefore, the purpose of this research is to examine and to model the precise effects a stress concentration will have on a specimen made of a generic Ni-base superalloy. The effects of non-isothermal loading will be studied, and …
Numerical Simulation Of Fracture Of A Nano-Paper Coated E-Glass/Polyester Composite With Thermal Damage, Zachary Graham
Numerical Simulation Of Fracture Of A Nano-Paper Coated E-Glass/Polyester Composite With Thermal Damage, Zachary Graham
HIM 1990-2015
Aerospace research for next-generation travel increasingly focuses on the use of advanced composites to reduce weight and cost while retaining strength. One subset of materials with great potential is based on the combination of resin matrix and glass-fiber reinforcement. This research explores the application of a candidate nanopaper coating with a given composite. Prior research applied a set of given heat fluxes to the top surface of the composite for a set of given periods of time, and subsequently performed a 3-point flexural test to determine the elastic modulus for both the coated and uncoated composite for all of the …
Strategically Minded Dynamic Analysis Of Strategic Flight Bat Maneuvers, Marie Kaspryzk
Strategically Minded Dynamic Analysis Of Strategic Flight Bat Maneuvers, Marie Kaspryzk
HIM 1990-2015
CATD was not only adequate for analyzing the pursuit of erratically moving prey but also worked well when analyzing the pursuit of prey that remained stationary. It cannot be fully concluded that bats utilize the CATD strategy to successfully capture erratically flying prey. The angle remains relatively constant but does not exhibit a zero change in angle as by definition. The large forces experienced by the bat were seen when the bat began to rotate its body about its pitch axis or when the bat made a large turn. Moments were seen specifically when the bat began to bank into …
Mechanical Properties And Thermal Residual Stresses Of Zrb2-Sic Ceramic Composites For Hypersonic Vehicle Applications, Richard Stadelmann
Mechanical Properties And Thermal Residual Stresses Of Zrb2-Sic Ceramic Composites For Hypersonic Vehicle Applications, Richard Stadelmann
Electronic Theses and Dissertations
Ultra High Temperature Ceramic (UHTC) ZrB2- 10, 20, 30wt%SiC composites are of high interest for use in hypersonic air-breathing vehicles. In this work, ZrB2- 10, 20, 30wt%SiC UHTC composites were produced by the Spark Plasma Sintering (SPS) technique. After sintering, almost dense ceramics with ~ 5-8% porosity were produced. Their mechanical properties, such as Young’s, shear, and bulk moduli, along with Poisson’s ratio, 4-point bending strength, and single edge V-notched beam (SEVNB) fracture toughness were measured. In addition, in-situ bending experiments under a Raman microscope were performed to determine the piezo-spectroscopic coefficients of SiC Raman active peaks for calculation of …
Bio-Inspired Cooperative Optimal Trajectory Planning For Autonomous Vehicles, Charles Remeikas
Bio-Inspired Cooperative Optimal Trajectory Planning For Autonomous Vehicles, Charles Remeikas
Electronic Theses and Dissertations
With the recent trend for systems to be more and more autonomous, there is a growing need for cooperative trajectory planning. Applications that can be considered as cooperative systems such as surveying, formation flight, and traffic control need a method that can rapidly produce trajectories while considering all of the constraints on the system. Currently most of the existing methods to handle cooperative control are based around either simple dynamics and/or on the assumption that all vehicles have homogeneous properties. In reality, typical autonomous systems will have heterogeneous, nonlinear dynamics while also being subject to extreme constraints on certain state …
Vision-Based Sensing And Optimal Control For Low-Cost And Small Satellite Platforms, Bradley Sease
Vision-Based Sensing And Optimal Control For Low-Cost And Small Satellite Platforms, Bradley Sease
Electronic Theses and Dissertations
Current trends in spacecraft are leading to smaller, more inexpensive options whenever possible. This shift has been primarily pursued for the opportunity to open a new frontier for technologies with a small financial obligation. Limited power, processing, pointing, and communication capabilities are all common issues which must be considered when miniaturizing systems and implementing low-cost components. This thesis addresses some of these concerns by applying two methods, in attitude estimation and control. Additionally, these methods are not restricted to only small, inexpensive satellites, but offer a benefit to large-scale spacecraft as well. First, star cameras are examined for the tendency …
Mission Analysis For Pico-Scale Satellite Based Dust Detection In Low Earth Orbits, Jacob Belli
Mission Analysis For Pico-Scale Satellite Based Dust Detection In Low Earth Orbits, Jacob Belli
Electronic Theses and Dissertations
A conceptual dust detection mission, KnightSat III, using pico-scale satellites is analyzed. The purpose of the proposed KnightSat III mission is to aid in the determination of the size, mass, distribution, and number of dust particles in low earth orbits through a low cost and flexible satellite or a formation of satellites equipped with a new dust detector. The analysis of a single satellite mission with an on-board dust detector is described; though this analysis can easily be extended to a formation of pico-scale satellites. Many design aspects of the mission are discussed, including orbit analysis, power management, attitude determination …
Vision-Based Testbeds For Control System Applicaitons, Robert Sivilli
Vision-Based Testbeds For Control System Applicaitons, Robert Sivilli
Electronic Theses and Dissertations
In the field of control systems, testbeds are a pivotal step in the validation and improvement of new algorithms for different applications. They provide a safe, controlled environment typically having a significantly lower cost of failure than the final application. Vision systems provide nonintrusive methods of measurement that can be easily implemented for various setups and applications. This work presents methods for modeling, removing distortion, calibrating, and rectifying single and two camera systems, as well as, two very different applications of vision-based control system testbeds: deflection control of shape memory polymers and trajectory planning for mobile robots. First, a testbed …
Surface Measurements And Predictions Of Full-Coverage Film Cooling, Gregory Natsui
Surface Measurements And Predictions Of Full-Coverage Film Cooling, Gregory Natsui
Electronic Theses and Dissertations
Full-coverage film cooling is investigated both experimentally and numerically. First, surface measurements local of adiabatic film cooling effectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-ε and SST k-ω, and their ability to predict local film cooling effectiveness throughout a full-coverage array. The objective of the experimental study is the quantification of local heat transfer augmentation and adiabatic film cooling effectiveness for four surfaces cooled by large, both in hole count and in non-dimensional spacing, arrays of film cooling holes. The four arrays are of …
Agglomeration, Evaporation And Morphological Changes In Droplets With Nanosilica And Nanoalumina Suspensions In An Acoustic Field, Erick Tijerino
Agglomeration, Evaporation And Morphological Changes In Droplets With Nanosilica And Nanoalumina Suspensions In An Acoustic Field, Erick Tijerino
Electronic Theses and Dissertations
Acoustic levitation permits the study of droplet dynamics without the effects of surface interactions present in other techniques such as pendant droplet methods. Despite the complexities of the interactions of the acoustic field with the suspended droplet, acoustic levitation provides distinct advantages of controlling morphology of droplets with nanosuspensions post precipitation. Droplet morphology is controlled by vaporization, deformation and agglomeration of nanoparticles, and therefore their respective timescales are important to control the final shape. The balance of forces acting on the droplet, such as the acoustic pressure and surface tension, determine the geometry of the levitated droplet. Thus, the morphology …
Thermal Stability Characteristics Of Fisher-Tropsch And Hydroprocessed Alternative Aviation Fuels In A Fixed Bed Reactor, Sergio Quintero
Thermal Stability Characteristics Of Fisher-Tropsch And Hydroprocessed Alternative Aviation Fuels In A Fixed Bed Reactor, Sergio Quintero
Electronic Theses and Dissertations
Growing prices, limited supply, and public concern about greenhouse gases associated with crude-derived jet fuels have led to development of renewable alternatives which must be compatible with the worldwide civilian and military aviation infrastructure, which were designed for operation with Jet-A/JP-8. Any alternative fuel should not have negative effects on the aircraft engines and fuel systems, especially from a thermal stability perspective, since any adverse effect of the physical properties, and chemical composition, including existence of trace elements, of those fuels may only be revealed after extensive operation, resulting in higher life-cycle maintenance and operation costs. This study considered four …
Vortex Tilting And The Enhancement Of Spanwise Flow In Flapping Wing Flight, Spencer Frank
Vortex Tilting And The Enhancement Of Spanwise Flow In Flapping Wing Flight, Spencer Frank
HIM 1990-2015
In summary the tilting mechanism helps to explain the overall flow structure and the stability of the leading edge vortex.; The leading edge vortex has been identified as the most critical flow structure for producing lift in flapping wing flight. Its stability depends on the transport of the entrained vorticity into the wake via spanwise flow. This study proposes a hypothesis for the generation and enhancement of spanwise flow based on the chordwise vorticity that results from the tilting of the leading edge vortex and trailing edge vortex. We investigate this phenomenon using dynamically scaled robotic model wings. Two different …
Optimal Attitude Control Management For A Cubesat, Michael James Develle
Optimal Attitude Control Management For A Cubesat, Michael James Develle
Electronic Theses and Dissertations
CubeSats have become popular among universities, research organizations, and government agencies due to their low cost, small size, and light weight. Their standardized configurations further reduce the development time and ensure more frequent launch opportunities. Early cubesat missions focused on hardware validation and simple communication missions, with little requirement for pointing accuracy. Most of these used magnetic torque rods or coils for attitude stabilization. However, the intrinsic problems associated with magnetic torque systems, such as the lack of three-axis control and low pointing accuracy, make them unsuitable for more advanced missions such as detailed imaging and on-orbit inspection. Threeaxis control …
Enhancing Cnt-Composites With Raman Spectroscopy, Gregory J. Freihofer
Enhancing Cnt-Composites With Raman Spectroscopy, Gregory J. Freihofer
Electronic Theses and Dissertations
Carbon Nanotubes (CNTs) have been the subject of intense research for their potential to improve a variety of material properties when developed as nano-composites. This research aims to address the challenges that limit the ability to transfer the outstanding nano-scale properties of CNTs to bulk nano-composites through Raman characterization. These studies relate the vibrational modes to microstructural characterization of CNT composites including stress, interface behavior, and defects. The formulation of a new fitting procedure using the pseudo-Voigt function is presented and shown to minimize the uncertainty of characteristics within the Raman G and D doublet. Methods for optimization of manufacturing …
Thermomechanical Behavior Of High-Temperature Shape Memory Alloy Ni-Ti-Pd-Pt Actuators, Douglas E. Nicholson
Thermomechanical Behavior Of High-Temperature Shape Memory Alloy Ni-Ti-Pd-Pt Actuators, Douglas E. Nicholson
Electronic Theses and Dissertations
To date the commercial use of shape memory alloys (SMAs) has been mostly limited to binary NiTi alloys with transformation temperatures approximately in the -100 to 100 ºC range. In an ongoing effort to develop high-temperature shape memory alloys (HTSMAs), ternary and quaternary additions are being made to binary NiTi to form NiTi-X (e.g., X: Pd, Pt, Au and Hf) alloys. Stability and repeatability can be further increased at these higher temperatures by limiting the stress, but the tradeoff is reduced work output and stroke. However, HTSMAs operating at decreased stresses can still be used effectively in actuator applications that …
An Experimental Investigation On The Dynamics Of Bubbles Utilizing Refrigerant R134a Under Pressurized Flow Boiling Conditions, Keon Vereen
Electronic Theses and Dissertations
Flow boiling heat transfer allows for the dissipation of large amounts of heat. In this work, the effect of heat flux and pressure on flow boiling of liquid refrigerant R-134a is studied in a vertical thin channel. The experimental setup mimics a refrigeration cycle and specifically looks at the effect of pressure and wall heat flux on the departure size and bubble generation rate. The experimental setup consists of a closed loop which includes a vertical narrow rectangular channel and two synchronized high speed cameras for optical measurements at either sides of the channel. The setup is built to employ …
Cfd Analysis Of A Uni-Directional Impulse Turbine For Wave Energy Conversion, Carlos Alberto Velez
Cfd Analysis Of A Uni-Directional Impulse Turbine For Wave Energy Conversion, Carlos Alberto Velez
Electronic Theses and Dissertations
Ocean energy research has grown in popularity in the past decade and has produced various designs for wave energy extraction. This thesis focuses on the performance analysis of a uni-directional impulse turbine for wave energy conversion. Uni-directional impulse turbines can produce uni-directional rotation in bi-directional flow, which makes it ideal for wave energy extraction as the motion of ocean waves are inherently bi-directional. This impulse turbine is currently in use in four of the world’s Oscillating Wave Columns (OWC). Current research to date has documented the performance of the turbine but little research has been completed to understand the flow …
Super-Adiabatic Combustion In Porous Media With Catalytic Enhancement For Thermoelectric Power Conversion, Kyle Thomas Mueller
Super-Adiabatic Combustion In Porous Media With Catalytic Enhancement For Thermoelectric Power Conversion, Kyle Thomas Mueller
Electronic Theses and Dissertations
The combustion of ultra-lean fuel to air mixtures provides an efficient way to convert the chemical energy of hydrocarbons into useful power. Conventional burning techniques of a mixture have defined flammability limits beyond which a flame cannot self-propagate due to heat losses. Matrix stabilized porous medium combustion is an advanced technique in which a solid porous matrix within the combustion chamber accumulates heat from the hot gaseous products and preheats incoming reactants. This heat recirculation extends the standard flammability limits and allows the burning of ultra-lean fuel mixtures, conserving energy resources, or the burning of gases of low calorific value, …
An Uncertainty Quantification Of The Variation Of Internal Heat Transfer Coefficients And The Effect On Airfoil Life, Jan H. Marsh
An Uncertainty Quantification Of The Variation Of Internal Heat Transfer Coefficients And The Effect On Airfoil Life, Jan H. Marsh
Electronic Theses and Dissertations
Uncertainty in accurately knowing applied internal heat transfer coefficients inside of a cooling passage can lead to variability in predicting low cycle fatigue life of a turbine vane or blade. Under-predicting a life value for a turbine part can have disastrous effects on the engine as a whole, and can negate efforts in innovative design for advanced cooling techniques for turbine components. Quantification of this fatigue life uncertainty utilizing a computational framework is the primary objective of this thesis. Through the use of probabilistic design methodologies a process is developed to simulate uncertainties of internal heat transfer coefficient, which are …
Thermal Performance Of Cryogenic Multilayer Insulation At Various Layer Spacings, Wesley Louis Johnson
Thermal Performance Of Cryogenic Multilayer Insulation At Various Layer Spacings, Wesley Louis Johnson
Electronic Theses and Dissertations
Multilayer insulation (MLI) has been shown to be the best performing cryogenic insulation system at high vacuum (less than 10-3 torr), and is widely used on spaceflight vehicles. Over the past 50 years, many numerous investigations of MLI have yielded a general understanding of the many variables associated with MLI. MLI has been shown to be a function of variables such as warm boundary temperature, the number of reflector layers, and the spacer material in between reflectors, the interstitial gas pressure and the interstitial gas. Because conduction between reflectors increases with the thickness of the spacer material, and yet the …