Non-Linear Magnetosphere-Ionosphere Interactions At High Latitudes, 2019 Embry Riddle Aeronautical University
Non-Linear Magnetosphere-Ionosphere Interactions At High Latitudes, Beket Tulegenov
PhD Dissertations and Master's Theses
Non-linear, 3D electromagnetic coupling between the ionosphere and magnetosphere is investigated in this dissertation. The study is based on a non-linear, 3D, reduced magnetohydrodynamic model describing interaction between dispersive Alfven waves and the nightside high-latitude ionosphere. Results are presented from a numerical study of small-scale, intense magnetic field-aligned currents observed in the vicinity of the discrete auroral arc by the Magnetosphere-Ionosphere Coupling in the Alfven Resonator (MICA) sounding rocket launched from Poker Flat, Alaska, on 19 February 2012. The goal of the MICA project was to investigate the hypothesis that such currents can be produced inside the ionospheric Alfven resonator ...
Wireless Antenna Detection Of Electrostatic Discharge Events, 2019 Utah State University
Wireless Antenna Detection Of Electrostatic Discharge Events, Allen Andersen, Jr Dennison
Wireless intraspacecraft communication technology is being developed for signal transfer on space missions to save weight and simplify the design. One consideration for this new technology is its interaction with space environmentinduced electrostatic discharges (ESDs). The short time scales of spacecraft ESD events result in broad frequency band signals that can interact with high-frequency wireless antennas. These interactions present a source of signal noise. However, they also present a possibility of in-flight wireless ESD monitoring. We present laboratory measurements of arcing on common spacecraft insulators using commercially available single-band 2.4-GHz and dual-band 2.4-/5.8-GHz Wi-Fi antennas. These ...
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, 2019 Utah State University
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, Brian Wood, Jordan Lee, Gregory Wilson, T. -C. Shen, Jr Dennison
Total, secondary, and backscatter electron yield data were taken with beam energies between 15 eV and 30 keV, in conjunction with energy emission data, to determine the extent of suppression of yield caused by carbon nanotube (CNT) forest coatings on substrates. CNT forests can potentially lower substrate yield due to both its inherently low-yield, low-atomic number (Z) carbon composition, and its bundled, high-aspect ratio structure. Rough surfaces, and in particular, surfaces with deep high-aspect-ratio voids, can suppress yields, as the electrons emitted from lower lying surfaces are recaptured by surface protrusions rather than escaping the near-surface region. Yields of multilayered ...
Optoelectronic Properties Of Methyl-Terminated Germanane, 2019 Sorbonne Université
Optoelectronic Properties Of Methyl-Terminated Germanane, Clément Livache, Bradley J. Ryan, Utkarsh Ramesh, Violette Steinmetz, Charlie Gréboval, Audrey Chu, Thibault Brule, Sandrine Ithurria, Geoffrey Prévot, Thierry Barisien, Abdelkarim Ouerghi, Matthew G. Panthani, Emmanuel Lhuillier
Chemical and Biological Engineering Publications
Germanane is a two-dimensional, strongly confined form of germanium. It presents an interesting combination of (i) ease of integration with CMOS technology, (ii) low toxicity, and (iii) electronic confinement which transforms the indirect bandgap of the bulk material into a direct bandgap featuring photoluminescence. However, the optoelectronic properties of this material remain far less investigated than its structural properties. Here, we investigate the photoluminescence and transport properties of arrays of methyl-terminated germanane flakes. The photoluminescence appears to have two contributions, one from the band edge and the other from trap states. The dynamics of the exciton appear to be in ...
Investigating Ions’ Effects On The Fluorescent Protein Dendra2, 2019 University of Maine
Investigating Ions’ Effects On The Fluorescent Protein Dendra2, Benjamin Waterman
While superresolution microscopy has opened the doors to insights into biological phenomena we couldn’t have dreamed of in the last century, its methodology is naturally limited. We aim to push the envelope of its capabilities by testing the effect that Ca2+ and H+ ions have on the fluorescent protein Dendra2. Utilizing a newly designed perfusion chamber, we flow separate solutions containing Ca2+ and H+ ions into a cellular environment, in which the cells in question have been tagged with Dendra2. Utilizing the superresolution technique known as Spectral Fluorescence Photoactivation Localization Microscopy, we are able to obtain information about the ...
Interplay Between Superconductivity And Itinerant Magnetism In Underdoped Ba1−Xkxfe2as2 (X = 0.2) Probed By The Response To Controlled Point-Like Disorder, 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 ...
Magnetocaloric Effect Of Micro- And Nanoparticles Of Gd5si4, 2019 Virginia Commonwealth University
Magnetocaloric Effect Of Micro- And Nanoparticles Of Gd5si4, S. M. Harstad, A. A. El-Gendy, Shalabh Gupta, Vitalij K. Pecharsky, R. L. Hadimani
Ames Laboratory Accepted Manuscripts
Materials exhibiting a large magnetocaloric effect (MCE) at or near room temperature are critical for solid-state refrigeration applications. The MCE is described by a change in entropy (ΔSM) and/or temperature (ΔTad) of a material in response to a change in applied magnetic field. Ball milled materials generally exhibit smaller ΔSM values compared to bulk; however, milling broadens the effect, potentially increasing the relative cooling power (RCP). The as-cast Gd5Si4 is an attractive option due to its magnetic transition at 340 K and associated MCE. Investigation of effect of particles size and transition temperature ...
Investigation Of Fundamental Principles Of Rigid Body Impact Mechanics, 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 ...
Improving 3d Printed Prosthetics With Sensors And Motors, 2019 Bridgewater College
Improving 3d Printed Prosthetics With Sensors And Motors, Rachel Zarin
A 3D printed hand and arm prosthetic was created from the idea of adding bionic elements while keeping the cost low. It was designed based on existing models, desired functions, and materials available. A tilt sensor keeps the hand level, two motors move the wrist in two different directions, a limit switch signals the fingers to open and close, and another motor helps open and close the fingers. All sensors and motors were built on a circuit board, programmed using an Arduino, and powered by a battery. Other supporting materials include metal brackets, screws, guitar strings, elastic bands, small clamps ...
In Situ Tem Study Of The Transitions Between Crystalline Si And Nonstoichiometric Amorphous Oxide Under Bipolar Voltage Bias, Xinchun Tian, Tao Ma, Lin Zhou, Geoff Brennecka, Xiaoli Tan
Materials Science and Engineering Publications
The electrical responses, either structurally or chemically, at the interface between a SiO2 thin film and a single crystalline Si substrate are an important research subject in Si-based devices. Dielectric breakdown-induced epitaxial migration of Si into SiO2 has been reported as a degradation mechanism in field effect transistors. Here, we show a direct observation of electric field induced conversion of single crystalline Si to nonstoichiometric amorphous oxide starting from the Si/native oxide interface using in situ transmission electron microscopy. We further show that nanocrystalline Si can form in the amorphous oxide under a voltage bias of reversed polarity. Electron ...
Interaction Dynamics Between Ferroelectric And Antiferroelectric Domains In A Pbzro3-Based Ceramic, 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, 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 ...
An Investigation Of The Anomalous Thrust Capabilities Of The Electromagnetic Drive, 2019 California Polytechnic State University, San Luis Obispo
An Investigation Of The Anomalous Thrust Capabilities Of The Electromagnetic Drive, Hannah J. Simons
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 ...
Slow Light With Interleaved P-N Junction To Enhance Performance Of Integrated Mach-Zehnder Silicon Modulators, 2019 Dept. of Physics, University of Pavia, Pavia, Italy
Slow Light With Interleaved P-N Junction To Enhance Performance Of Integrated Mach-Zehnder Silicon Modulators, Marco Passoni, Dario Gerace, Liam O'Faolain, Lucio Claudio Andreani
Slow light is a very important concept in nanophotonics, especially in the context of photonic crystals. In this work, we apply our previous design of band-edge slow light in silicon waveguide gratings [M. Passoni et al, Opt. Express 26, 8470 (2018)] to Mach-Zehnder modulators based on the plasma dispersion effect. The key idea is to employ an interleaved p-n junction with the same periodicity as the grating, in order to achieve optimal matching between the electromagnetic field profile and the depletion regions of the p-n junction. The resulting modulation efficiency is strongly improved as compared to common modulators based on ...
Exact Feedback Linearization Of Systems With State-Space Modulation And Demodulation, 2019 University of New Orleans
Exact Feedback Linearization Of Systems With State-Space Modulation And Demodulation, Nikolaos I. Xiros Deng
University of New Orleans Theses and Dissertations
The control theory of nonlinear systems has been receiving increasing attention in recent years, both for its technical importance as well as for its impact in various fields of application. In several key areas, such as aerospace, chemical and petrochemical industries, bioengineering, and robotics, a new practical application for this tool appears every day. System nonlinearity is characterized when at least one component or subsystem is nonlinear. Classical methods used in the study of linear systems, particularly superposition, are not usually applied to the nonlinear systems. It is necessary to use other methods to study the control of these systems ...
Multifunctional Properties Of Gan Nws Applied To Nanometrology, Nanophotonics, And Scanning Probe Microscopy/Lithography, 2019 University of New Mexico
Multifunctional Properties Of Gan Nws Applied To Nanometrology, Nanophotonics, And Scanning Probe Microscopy/Lithography, Mahmoud Behzadirad
Optical Science and Engineering ETDs
GaN nanowires are promising for optical and optoelectronic applications because of their waveguiding properties and large optical bandgap. Recent researches have shown superior mechanical properties of GaN nanowires which promises their use in new research areas e.g. nanometrology. In this work, we develop a scalable two-step top-down approach using interferometric lithography as well a bottom-up growth of NWs using MOCVD, to manufacture highly-ordered arrays of nanowires with atomic surface roughness and desired aspect-ratios to be used in nanophotonics and atomic precision metrology and lithography. Using this method, uniform nanowire arrays were achieved over large-areas (~1 mm2) with aspect-ratio ...
High Resolution Validation Of Next Generation Turbulent Flow Models Using Neutron Beams, Laser Fluorescence, And Cryogenic Helium, 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, 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 ...
Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, 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 ...
Feedforward And Feedback Signals In The Olfactory System, 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 ...