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Nonlinear Estimation And Control Methods For Mechanical And Aerospace Systems Under Actuator Uncertainty, Krishna Bhavithavya Kidambi 2019 Embry-Riddle Aeronautical University

Nonlinear Estimation And Control Methods For Mechanical And Aerospace Systems Under Actuator Uncertainty, Krishna Bhavithavya Kidambi

Dissertations and Theses

Air flow velocity field control is of crucial importance in aerospace applications to prevent the potentially destabilizing effects of phenomena such as cavity ow oscillations, flow separation, flow-induced limit cycle oscillations (LCO) (flutter), vorticity, and acoustic instabilities. Flow control is also important in aircraft applications to reduce drag in aircraft wings for improved flight performance. Although passive flow control approaches are often utilized due to their simplicity, active flow control (AFC) methods can achieve improved flight performance over a wider range of time-varying operating conditions by automatically adjusting their level of control actuation in response to real-time sensor measurements. Although ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Paul C. Canfield

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee 2019 University of Connecticut

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Paul C. Canfield

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, Ruslan Prozorov, Marcin Kończykowski, Makariy A. Tanatar, Hai-Hu Wen, Rafael M. Fernandes, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

The response of superconductors to controlled introduction of point-like disorder is an important tool to probe their microscopic electronic collective behavior. In the case of iron-based superconductors, magnetic fluctuations presumably play an important role in inducing high-temperature superconductivity. In some cases, these two seemingly incompatible orders coexist microscopically. Therefore, understanding how this unique coexistence state is affected by disorder can provide important information about the microscopic mechanisms involved. In one of the most studied pnictide family, hole-doped Ba1−xKxFe2As2 (BaK122), this coexistence occurs over a wide range of doping levels, 0.16 ≲ x ≲ 0.25. We used ...


Investigation Of Fundamental Principles Of Rigid Body Impact Mechanics, Khalid Alluhydan 2019 Southern Methodist University

Investigation Of Fundamental Principles Of Rigid Body Impact Mechanics, Khalid Alluhydan

Mechanical Engineering Research Theses and Dissertations

In impact mechanics, the collision between two or more bodies is a common, yet a very challenging problem. Producing analytical solutions that can predict the post-collision motion of the colliding bodies require consistent modeling of the dynamics of the colliding bodies. This dissertation presents a new method for solving the two and multibody impact problems that can be used to predict the post-collision motion of the colliding bodies. Also, we solve the rigid body collision problem of planar kinematic chains with multiple contacts with external surfaces.

In the first part of this dissertation, we study planar collisions of Balls and ...


Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan 2019 Iowa State University

Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan

Xiaoli Tan

The antiferroelectric-ferroelectric phase transition in PbZrO3-based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is ...


Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan 2019 Iowa State University

Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, Zhongming Fan, Fei Xue, Goknur Tutuncu, Long-Qing Chen, Xiaoli Tan

Materials Science and Engineering Publications

The antiferroelectric-ferroelectric phase transition in PbZrO3-based oxides is of both fundamental and practical importance. In ceramics in which such a transition readily occurs, the antiferroelectric and the ferroelectric phases often coexist in individual grains with a coherent interphase interface. In this work, the electric biasing in situ transmission electron microscopy technique is employed to directly observe a unique microstructural dynamic when ferroelectric and antiferroelectric domains are driven by a moderate electric field to interact. It is found that, under monotonic loading, the ferroelectric domain grows until it is blocked by the ferroelectric-antiferroelectric interface. At the same time, a kink is ...


Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee 2019 University of Connecticut

Ultrahigh Elastically Compressible And Strain-Engineerable Intermetallic Compounds Under Uniaxial Mechanical Loading, Gyuho Song, Vladislav Borisov, William Meier, Mingyu Xu, Keith J. Dusoe, John T. Sypek, Roser Valentí, Paul C. Canfield, Seok-Woo Lee

Ames Laboratory Accepted Manuscripts

Intermetallic compounds possess unique atomic arrangements that often lead to exceptional material properties, but their extreme brittleness usually causes fracture at a limited strain of less than 1% and prevents their practical use. Therefore, it is critical for them to exhibit either plasticity or some form of structural transition to absorb and release a sufficient amount of mechanical energy before failure occurs. This study reports that the ThCr2Si2-structured intermetallic compound (CaFe2As2) and a hybrid of its structure (CaKFe4As4) with 2 µm in diameter and 6 µm in height can exhibit superelasticity with strain up to 17% through a reversible, deformation-induced ...


Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan 2019 Iowa State University

Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan

Xiaoli Tan

(Bi 1/2Na 1/2)TiO 3-based solid solutions, one of the major systems of lead-free piezoelectric ceramics, exhibit a low thermal depolarization temperature ( T d~100°C). It was reported that by incorporating 30 mol% ZnO particles to form a ceramic composite of (Bi 1/2Na 1/2) 0.94Ba 0.06TiO 3/ZnO, the depolarization process can be shifted up to ~250 °C. In the present work, a variety of advanced transmission electron microscopy techniques, including in situ heating, annular bright-field, high-angle annular dark-field, geometric phase analysis, energy-dispersive spectrum and electron energy-loss spectroscopy, are employed to investigate the ...


An Investigation Of The Anomalous Thrust Capabilities Of The Electromagnetic Drive, Hannah J. Simons 2019 California Polytechnic State University, San Luis Obispo

An Investigation Of The Anomalous Thrust Capabilities Of The Electromagnetic Drive, Hannah J. Simons

Physics

The Electromagnetic Drive (EMDrive) is a propellant-less engine concept hypothesized by aero- space engineer Roger Shawyer. Shawyer’s proposed thruster technology is grounded on the theory of electromagnetic resonant behavior exhibited by a radiofrequency cavity, though the source of any generated thrust is undetermined by current physical laws. NASA Eagleworks Laboratories at John- son Space Center conducted a vacuum test campaign to investigate previously reported anomalous thrust capabilities of such a closed radiofrequency cavity, using a low-thrust torsion pendulum. The team published positive, although small-scaled thrust results in 2017. Following NASA Eagleworks breakthrough result and operating under the assumption that ...


High Resolution Validation Of Next Generation Turbulent Flow Models Using Neutron Beams, Laser Fluorescence, And Cryogenic Helium, Landen G Mcdonald 2019 University of Tennessee, Knoxville

High Resolution Validation Of Next Generation Turbulent Flow Models Using Neutron Beams, Laser Fluorescence, And Cryogenic Helium, Landen G Mcdonald

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Turbulent fluid flow is an incredibly unpredictable subject that continues to confound scientists and engineers. All of the empirical data that has been the basis of conventional turbulent computational fluid dynamics (CFD) models for decades only extends to roughly the equivalent turbulence created when Michael Phelps swims in a pool. The problem is that this data is then extrapolated out many orders of magnitude in order to design cruise ships, airplanes, and rockets which operate in significantly more turbulent flow regimes. This creates an incredible degree of uncertainty in the design process that demands over-engineering and increased expenditures.

The development ...


Autonomous Watercraft Simulation And Programming, Nicholas J. Savino 2019 Lynchburg College

Autonomous Watercraft Simulation And Programming, Nicholas J. Savino

Undergraduate Theses and Capstone Projects

Automation of various modes of transportation is thought to make travel more safe and efficient. Over the past several decades advances to semi-autonomous and autonomous vehicles have led to advanced autopilot systems on planes and boats and an increasing popularity of self-driving cars. We simulated the motion of an autonomous vehicle using computational models. The simulation models the motion of a small-scale watercraft, which can then be built and programmed using an Arduino Microcontroller. We examined different control methods for a simulated rescue craft to reach a target. We also examined the effects of different factors, such as various biases ...


Feedforward And Feedback Signals In The Olfactory System, Srimoy Chakraborty 2019 University of Arkansas, Fayetteville

Feedforward And Feedback Signals In The Olfactory System, Srimoy Chakraborty

Theses and Dissertations

The conglomeration of myriad activities in neural systems often results in prominent oscillations. The primary goal of the research presented in this thesis was to study effects of sensory stimulus on the olfactory system of rats, focusing on the olfactory bulb (OB) and the anterior piriform cortex (aPC). Extracellular electrophysiological measurements revealed distinct frequency bands of oscillations in OB and aPC. However, how these oscillatory fluctuations help the animal to process sensory input is not clearly understood. Here we show high frequency oscillations in olfactory bulb carry feedforward signals to anterior piriform cortex whereas feedback from the aPC is predominantly ...


Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller 2019 University of Arkansas, Fayetteville

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller

Theses and Dissertations

Materials with features at the nanoscale can provide unique mechanical properties and increased functionality when included as part of a nanocomposite. This dissertation utilizes computational methods at multiple scales, including molecular dynamics (MD) and density functional theory (DFT), and the coupled atomistic and discrete dislocation multiscale method (CADD), to predict the mechanical properties of nanocomposites possessing nanomaterials that are either 1-D (carbyne chains), 2-D (graphene sheets), or 3-D (Al/amorphous-Si core-shell nanorod).

The MD method is used to model Ni-graphene nanocomposites. The strength of a Ni-graphene nanocomposite is found to improve by increasing the gap between the graphene sheet and ...


Transferring Power Through A Magnetic Couple, Nickolas Cruz Villalobos Jr. 2019 Linfield College

Transferring Power Through A Magnetic Couple, Nickolas Cruz Villalobos Jr.

Senior Theses

Properties of several working magnetic coupled rotors have been measured and their performance compared to theoretical models. Axial magnetic couplers allow rotors to work within harsh environments, without the need for seals, proper alignment, or overload protection on a motor. The influence of geometrical parameters, such as distance from the center of the rotors, polarity arrangement, and the number of dipole pairs were experimentally tested. These results can be used to improve rotor designs, to increase strength and efficiency.


Construction Of An Auger Microscope, Charles Soulen 2019 William & Mary

Construction Of An Auger Microscope, Charles Soulen

Undergraduate Honors Theses

This thesis describes the design, adaptations and characterizations necessary to partially turn an Auger Electron Spectroscopy Instrument (AES) into an Auger Electron Microscope (AEM). The completed AEM will be able to scan and characterize materials over an area, unlike the AES which only took data from a single point. However, due to time constraints, this thesis only partially describes the creation of an AEM. We were able to show proof-of-concept, though, we were unable to run AEM on a material. We have also increased the theoretical accuracy of the instrument by replacing decades-old electronics with modern alternatives. Again, due to ...


Optical Response Analysis Of Thz Photoconductive Antenna Using Comsol Multiphysics, Jose Isaac Santos Batista 2019 University of Arkansas, Fayetteville

Optical Response Analysis Of Thz Photoconductive Antenna Using Comsol Multiphysics, Jose Isaac Santos Batista

Electrical Engineering Undergraduate Honors Theses

A THz photoconductive antenna consists of antenna pads laid over a photoconductive substrate. These types of antennas are excited through the application of an optical pump (laser), which generates carriers inside the semiconductor. The acceleration and recombination of these carriers produce photocurrent that excites the antenna and generates THz pulse. This thesis focuses on analyzing the optical response of a photoconductive antenna, which consist of the interaction of the incident electric field of a laser pump with the radiating device. It develops the amplitude modulation process of a plane wave of light into a laser pump. It also takes into ...


Characterization Of Hydride Vapor Phase Epitaxy Grown Gan Substrates For Future Iii-Nitride Growth, Alaa Ahmad Kawagy 2019 University of Arkansas, Fayetteville

Characterization Of Hydride Vapor Phase Epitaxy Grown Gan Substrates For Future Iii-Nitride Growth, Alaa Ahmad Kawagy

Theses and Dissertations

The aim of this research is to investigate and characterize the quality of commercially obtained gallium nitride (GaN) on sapphire substrates that have been grown using hydride vapor phase epitaxy (HVPE). GaN substrates are the best choice for optoelectronic applications because of their physical and electrical properties. Even though HVPE GaN substrates are available at low-cost and create the opportunities for growth and production, these substrates suffer from large macro-scale defects on the surface of the substrate.

In this research, four GaN on sapphire substrates were investigated in order to characterize the surface defects and, subsequently, understand their influence on ...


Modeling Multiphase Flow And Substrate Deformation In Nanoimprint Manufacturing Systems, Andrew Cochrane 2019 University of New Mexico

Modeling Multiphase Flow And Substrate Deformation In Nanoimprint Manufacturing Systems, Andrew Cochrane

Nanoscience and Microsystems ETDs

Nanopatterns found in nature demonstrate that macroscopic properties of a surface are tied to its nano-scale structure. Tailoring the nanostructure allows those macroscopic surface properties to be engineered. However, a capability-gap in manufacturing technology inhibits mass-production of nanotechnologies based on simple, nanometer-scale surface patterns. This gap represents an opportunity for research and development of nanoimprint lithography (NIL) processes. NIL is a process for replicating patterns by imprinting a fluid layer with a solid, nano-patterned template, after which ultraviolet cure solidifies the fluid resulting in a nano-patterned surface. Although NIL has been demonstrated to replicate pattern features as small as 4 ...


Planar Ion Probe For Low-Latitude Ionosphere/Thermosphere Enhancements In Density Cubesat Mission, Liam Owen Gunter 2019 Embry-Riddle Aeronautical University

Planar Ion Probe For Low-Latitude Ionosphere/Thermosphere Enhancements In Density Cubesat Mission, Liam Owen Gunter

Dissertations and Theses

One of the crucial measurements for characterizing any space weather event is absolute plasma density and plasma density fluctuations, both spatially and temporally. Langmuir probes are the oldest and most proven instruments for these in-situ measurements. This thesis enumerates the development of a miniaturized low-noise Langmuir probe intended for a dual CubeSat mission to study equatorial temperature and wind anomaly in the Earth’s ionosphere.

The Langmuir probe instrument developed is of a planar geometry and fix biased in the ion saturation region, i.e. negative w.r.t. spacecraft chassis. Operating the Langmuir probe in the ion saturation region ...


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