Engineering Physics Commons^™

Infrasound Propagation In Terrestrial Planetary Atmospheres, Lynsey B. Schroeder

Doctoral Dissertations and Master's Theses

Acoustic waves in the infrasonic frequency range, that is below 10 Hertz, have been observed to propagate to high altitudes in Earth's atmosphere. These waves have many sources, both natural and artificial, such as seismic events, convective storm systems, and nuclear explosions. Here, we seek to better understand the characteristics of atmospheric infrasound- below 0.1 Hz in particular- so as to improve the ability to detect their presence and sources. It is well-known that ambient attributes of an atmosphere, such as temperature, density, and composition, directly affect the propagation and growth of waves, and therefore it is likely that these …

Molecular Sensitivity And Selectivity Of Metal Nanoparticles Decorated Graphene As ‘Smart’ Surface-Enhanced Raman Scattering (Sers) Platforms [Hybrid Poster 1-A], Alexander Banaszak, Tyler Smith

Posters-at-the-Capitol

Raman scattering signal enhancement that uses graphene as support, graphene-enhanced Raman scattering (GERS), is a recent phenomenon. It can produce clean and reproducible Raman signals of chemical molecules with significantly enhanced signal intensity in contrast to traditional surface- (SERS) and tip- enhanced Raman scattering (TERS) techniques. While enhancement in SERS and TERS arise due to the electromagnetic mechanism, GERS also relies on a chemical mechanism and therefore shows unique molecular sensitivity and selectivity. In this work, we developed graphene materials decorated with noble metal (silver and gold) nanoparticles for detection of different chemical molecules e.g. methylene blue (MB) and rhodamine …

Bio-Assembled Nano-Composites As High-Density Energy Storage Materials, Xixiang Zhang, Yingbang Yao

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Evolution Of Network Architecture In A Granular Material Under Compression, Lia Papadopoulous, James G. Puckett, Karen E. Daniels, Danielle S. Bassett

Physics and Astronomy Faculty Publications

As a granular material is compressed, the particles and forces within the system arrange to form complex and heterogeneous collective structures. Force chains are a prime example of such structures, and are thought to constrain bulk properties such as mechanical stability and acoustic transmission. However, capturing and characterizing the evolving nature of the intrinsic inhomogeneity and mesoscale architecture of granular systems can be challenging. A growing body of work has shown that graph theoretic approaches may provide a useful foundation for tackling these problems. Here, we extend the current approaches by utilizing multilayer networks as a framework for directly quantifying …

Evaluation Of Hydrothermally Synthesized Uranium Dioxide For Novel Semiconductor Applications, Christopher M. Young

Theses and Dissertations

Neutron radiation detection is an important part of the national strategy for nonproliferation efforts worldwide. Key to the success of these programs is detector material development which establishes the limits of efficiency, sensitivity, and power usage for a detector of practical use. This research focused upon the study of neutron detection using single crystal actinide compounds, specifically UO2, taking advantage of the successful hydrothermal synthesis of UO2 at the Air Force Research Laboratories. Initial indications are that this material may be of sufficient quality for semiconductor application.

Estimation Of Temporal Variations In Path-Averaged Atmospheric Refractive Index Gradient From Time-Lapse Imagery, Santasri Basu, Jack E. Mccrae, Steven T. Fiorino, Jared Przelomski

Faculty Publications

The sea level vertical refractive index gradient in the U.S. Standard Atmosphere model is −2.7×10⁻⁸  m⁻¹ at 500 nm. At any particular location, the actual refractive index gradient varies due to turbulence and local weather conditions. An imaging experiment was conducted to measure the temporal variability of this gradient. A tripod mounted digital camera captured images of a distant building every minute. Atmospheric turbulence caused the images to wander quickly, randomly, and statistically isotropically and changes in the average refractive index gradient along the path caused the images to move vertically and more slowly. The temporal variations of …

Local Writing Of Exchange Biased Domains In A Heterostructure Of Co/Pd Pinned By Magnetoelectric Chromia, Uday Singh, William Echtenkamp, M. Street, Christian Binek, Shireen Adenwalla

Shireen Adenwalla Papers

The writing of micrometer-scaled exchange bias domains by local, laser heating of a thin-film heterostructure consisting of a perpendicular anisotropic ferromagnetic Co/Pd multilayer and a (0001) oriented film of the magnetoelectric antiferromagnet Cr₂O₃ (chromia) is reported. Exchange coupling between chromia’s boundary magnetization and the ferromagnet leads to perpendicular exchange bias. Focused scanning magneto-optical Kerr measurements are used to measure local hysteresis loops and create a map of the exchange bias distribution as a function of the local boundary magnetization imprinted in the antiferromagnetic pinning layer on field cooling. The robust boundary magnetization of the Cr₂O …

Direct Bandgap Cross-Over Point Of Ge1-YSnY Grown On Si Estimated Through Temperature-Dependent Photoluminescence Studies, Thomas R. Harris, Mee-Yi Ryu, Yung Kee Yeo, Buguo Wang, C. L. Senaratne

Faculty Publications

Epitaxial Ge_1-ySn_y (y = 0%–7.5%) alloys grown on either Si or Ge-buffered Si substrates by chemical vapor deposition were studied as a function of Sn content using temperature-dependent photoluminescence (PL). PL emission peaks from both the direct bandgap (Γ-valley) and the indirect bandgap (L-valley) to the valence band (denoted by E_D and EID, respectively) were clearly observed at 125 and 175 K for most Ge_1-ySn_y samples studied. At 300 K, however, all of the samples exhibited dominant E_D emission with either very weak or no measureable E_ID emission. At 10 K, …

Preliminary Results From A Ground Based Magnetometer Rotation Table, Rachel Newman, April Gross, Jolene Johnson, Kaye Smith, Erick Agrimson, James Flaten

2017 Academic High Altitude Conference

Understanding high altitude balloon rotation is important for many types of scientific measurements, therefore, balloon and payload rotation is a continuing area of interest and research. In this work, we present results obtained from an Arduino logged magnetometer rotated on a ground based rotation table. This table allowed us to precisely rotate and locate the Arduino logged magnetometer. We compare the Arduino logged results with “known magnetic field orientation” using an AIM rocketry altimeter. This comparison allowed us to test the accuracy of our Arduino logged results and the sampling capabilities of our magnetometer system using different rotational speeds.

Abstracts From The 2016 Ahac Conference, Erick Agrimson

2017 Academic High Altitude Conference

This is a listing of Abstracts from AHAC 2016

Photoluminescence Measurement On Low-Temperature Metal Modulation Epitaxy Grown Gan, Yang Wu

Graduate Theses and Dissertations

A low-temperature photoluminescence (PL) study was conducted on low-temperature metal modulation epitaxy (MME) grown GaN. By comparing the PL signal from high temperature grown GaN buffer layers, and MME grown cap layers on top of the buffer layers, it was found that MME grown GaN cap has a significantly greater defect-related emission. The band edge PL from MME grown GaN found to be 3.51eV at low temperature. The binding energy of the exciton in GaN is determined to be 21meV through temperature dependence analysis. A PL peak at 3.29eV was found in the luminescence of the MME grown cap layer, …

Instrumentation Of A Self-Correcting Data Acquisition System For Ultrafast Lasers, Fabricio S. Marin

DePaul Discoveries

Optical phenomenon in semiconductors and other light-sensitive materials typically happen at very short time durations, and require instruments capable of measuring time resolutions on the order of nanoseconds to femtoseconds. Electronics can only measure up to nanosecond-time lengths. The purpose of this summer research project is to design a system capable of achieving variable time delays with resolutions up to femtosecond range to use in time-resolved experiments with the pump-probe technique. The time delay is achieved using a delay stage driven by a micro stepper-motor which moves in variable increments while an encoder counts the steps and tells a computer …

Experimental Investigation And Numerical Simulation Of A Copper Micro-Channel Heat Exchanger With Hfe-7200 Working Fluid, Eric Borquist

Doctoral Dissertations

Ever increasing cost and consumption of global energy resources has inspired the development of energy harvesting techniques which increase system efficiency, sustainability, and environmental impact by using waste energy otherwise lost to the surroundings. As part of a larger effort to produce a multi-energy source prototype, this study focused on the fabrication and testing of a waste heat recovery micro-channel heat exchanger. Reducing cost and facility requirements were a priority for potential industry and commercial adoption of such energy harvesting devices. During development of the micro-channel heat exchanger, a new fabrication process using mature technologies was created that reduced cost, …

Model For Computing Kinetics Of The Graphene Edge Epitaxial Growth On Copper, Mikhail Khenner

Mathematics Faculty Publications

A basic kinetic model that incorporates a coupled dynamics of the carbon atoms and dimers ona copper surface is used to compute growth of a single-layer graphene island. The speed of theisland's edge advancement on Cu[111] and Cu[100] surfaces is computed as a function of the growthtemperature and pressure. Spatially resolved concentration pro les of the atoms and dimers aredetermined, and the contributions provided by these species to the growth speed are discussed.Island growth in the conditions of a thermal cycling is studied.

Tunable Split-Ring Resonators Using Germanium Telluride, Christopher H. Kodama, Ronald Coutu Jr.

Faculty Publications

We demonstrate terahertz (THz) split-ring resonator (SRR) designs with incorporated germanium telluride (GeTe) thin films. GeTe is a chalcogenide that undergoes a nonvolatile phase change from the amorphous to crystalline state at approximately 200 °C, depending on the film thickness and stoichiometry. The phase change also causes a drop in the material's resistivity by six orders of magnitude. In this study, two GeTe-incorporated SRR designs were investigated. The first was an SRR made entirely out of GeTe and the second was a gold SRR structure with a GeTe film incorporated into the gap region of the split ring. These devices …

Model For The Electrolysis Of Water And Its Use For Optimization, Roger Lascorz, Javier E. Hasbun Dr

Georgia Journal of Science

The goal of this research was to study the optimization of the electrolysis of water both theoretically and experimentally. For accuracy, 3 hr experiments were made with measurements recorded every 15 min. The results show that a better model than the classical one is needed for water electrolysis. A new model that fits experimental data better is proposed. The results of this new model not only predict hydrogen production in electrolysis of water better, but show a way to predict gas production of any liquid as well as what voltage to use to optimize it.

Experimental Building Demonstration Model With Viscous Fluid Dampers, Blake Thomas Reeve, Brianna Jean Kufa, Aden Malek Stepanians, Sophie Carmion Ratkovich

Architectural Engineering

The Architectural Engineering major places a heavy emphasis on structural dynamics and the role of wind and seismic loading in building analysis and design. Buildings of high importance that are critical to community function, such as hospitals, often utilize supplemental damping devices like supplemental viscous fluid dampers or base isolators to reduce the overall demands on the structural system. The design and analysis of these dampers are typically not taught at the undergraduate level, and is frequently performed by mechanical engineers, in lieu of structural engineers.

To better understand and research building behavior with supplemental damping devices, our multi-disciplinary team …

Zno Thin Films Generated By Ex-Situ Thermal Oxidation Of Metallic Zn For Photovoltaic Applications, Kovas Zygas

Macalester Journal of Physics and Astronomy

ZnO thin films that function as either transparent conducting oxides in solid-state photovoltaic cells or as nanocrystalline dye-absorbers in dye-sensitized solar cells have the potential to reduce the cost of producing electricity from solar energy. Although there exist many methods to produce ZnO thin films, the most economical and practical method may be oxidation of metallic Zn thin films. This research examined the utility of ex-situ thermal oxidation of DC magnetron sputtered Zn thin films in generating useful ZnO thin films for these photovoltaic applications. We annealed Zn thin films in air at 570° C in order to produce ZnO …

Enhanced Adhesion Of Superhydrophobic Zno Surface, Liqiu Zheng Dr., Chan Kwaichow B.

Georgia Journal of Science

The superhydrophobicity and the strong solid-liquid adhesion of the dually structured ZnO surface are attributed to the suitable size of microstructure and nanostructure. This phenomenon, so different from the Lotus effect, can be called the Petal effect— the super hydrophobicity and the enhanced solid-liquid adhesion coexist on the same surface. The Cassie impregnating model was proposed to understand the underlying reason.

Reflective Efficiencies Of Materials For Applications Of Bifacial Solar Cells, Michael Metter

Senior Theses

The bifacial solar cell is superior to its monofacial predecessor due to its ability to convert both incident light on top and reflected light from below into energy. The scattering of the reflected light is affected by the property of the material on which it is interacting. To date, little work has been contributed to studying the properties of these materials to determine optimal quantities for bifacial solar cells. In the first experiment, reflective efficiencies compared to the angle of reflection were explored for different grit of sandpaper in order to develop an understanding of how surface texture impacts reflectivity. …

A New Take On Testing: Evaluating Design Systems In Response To The Recent Natural Disaster In Nepal, Jazmine L. Brown

Creative Activity and Research Day - CARD

In this thesis project I analyze the destruction of the 2015 earthquake in Nepal, specifically in the structural and architectural collapse. I have focused my research on the areas with greatest documented destruction and vulnerability, specifically Kathmandu and the settlements in the Middle Hills. The introduction of a new lateral testing mechanism can provided much needed information on the seismic strengths of vernacular construction methods.

Failure Of Surface Color Cues Under Natural Changes In Lighting, David H. Foster, Iván Marín-Franch

MODVIS Workshop

Color allows us to effortlessly discriminate and identify surfaces and objects by their reflected light. Although the reflected spectrum changes with the illumination spectrum, cone photoreceptor signals can be transformed to give useful cues for surface color. But what happens when both the spectrum and the geometry of the illumination change, as with lighting from the sun and sky? Is it possible, as a matter of principle, to obtain reliable cues by processing cone signals alone? This question was addressed here by estimating the information provided by cone signals from time-lapse hyperspectral radiance images of five outdoor scenes under natural …

Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill

Physics Undergraduate Honors Theses

Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …

The Evaluation And Implementation Of Magnetic Fields For Large Strain Uniaxial And Biaxial Cyclic Testing Of Magnetorheological Elastomers., Dave Gorman, Niall Murphy, Ray Ekins, Stephen Jerrams

Articles

Magnetorheological Elastomers (MREs) are “smart” materials whose physical properties are altered by the application of magnetic fields. In previous studies the properties of MREs have been evaluated under a variety of conditions, however little attention has been paid to the recording and reporting of the magnetic fields used in these tests [1]. Currently there is no standard accepted method for specifying the magnetic field applied during MRE testing. This study presents a detailed map of a magnetic field applied during MRE tests as well as providing the first comparative results for uniaxial and biaxial testing under high strain fatigue test …

Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill

Mechanical Engineering Undergraduate Honors Theses

Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …

Polytetraflouroethylene Thin Coatings For Tribological Applications, Samuel L. Jenkins

Physics Undergraduate Honors Theses

Mechanical components with lower coefficients of friction decrease the amount of energy dissipated by the system due to friction. Coating these components would decrease the coefficients of friction between surfaces without sacrificing the strength of the components. A polytetrafluoroethylene (PTFE) layer adhered through a polydopamine (PDA) layer on a steel substrate will reduce the coefficient of friction on the substrate surface. This paper discusses different methods for attempting to increase the uniformity of the PDA layer as well as decrease the PDA coating time. Methods for increasing uniformity include using a particle disperser instead of a magnet stir rod, changing …

Spontaneous Parametric Down Conversion Of Photons Through Β-Barium Borate, Luke Horowitz

Physics

An apparatus for detecting pairs of entangled 405nm photons that have undergone Spontaneous Parametric Down Conversion through β-Barium Borate is described. By using avalanche photo-diodes to detect the low-intensity converted beam and a coincidence module to register coincident photons, it is possible to create an apparatus than can be used to perform quantum information experiments under a budget appropriate for an undergraduate physics lab.

Particle Image Velocimetry Design & Installation, Zach Ritchie

Mechanical Engineering Undergraduate Honors Theses

This work will mainly focus on the design, construction, and installation of the Particle Image Velocimetry (PIV) system in the Chemical Hazards Research Center wind tunnel. The PIV system utilizes a Class IV (double pulsed) laser, optics to produce a light sheet, timing circuitry, and a high-resolution camera (with buffered output) to measure a system’s velocity (two-dimensional) field by determining the displacement of particles over the time between laser pulses. For maximum mobility and functionality, the PIV system was installed in the center of the tunnel on a moveable cart with the laser and camera mounted to an adjustable support. …

Experimental And Computational Studies Of Cortical Neural Network Properties Through Signal Processing, Wesley Patrick Clawson

Graduate Theses and Dissertations

Previous studies, both theoretical and experimental, of network level dynamics in the cerebral cortex show evidence for a statistical phenomenon called criticality; a phenomenon originally studied in the context of phase transitions in physical systems and that is associated with favorable information processing in the context of the brain. The focus of this thesis is to expand upon past results with new experimentation and modeling to show a relationship between criticality and the ability to detect and discriminate sensory input. A line of theoretical work predicts maximal sensory discrimination as a functional benefit of criticality, which can then be characterized …

Spin Polarisation Oft ̄Tγγproduction At Nlo+Ps With Gosam Interfaced To Madgraph5_Amc@Nlo, Hans Van Deurzen, Rikkert Frederix, Valentin Hirschi, Gionata Luisoni, Pierpaolo Mastrolia, Giovanni Ossola

Publications and Research

We present an interface between the multipurpose Monte Carlo toolMadGraph5_aMC@NLOand the automated amplitude generator GoSam. As a first application of this novel framework, we compute the NLO corrections topp→t ̄tHandpp→t ̄tγγmatched to a parton shower. In the phenomenological analyses of these processes, we focus our attention on observables which are sensitive to the polarisation of the top quarks.