Physics Commons^™

New Methodologies For Examining And Supporting Student Reasoning In Physics, John C. Speirs

Electronic Theses and Dissertations

Learning how to reason productively is an essential goal of an undergraduate education in any STEM-related discipline. Many non-physics STEM majors are required to take introductory physics as part of their undergraduate programs. While certain physics concepts and principles may be of use to these students in their future academic careers and beyond, many will not. Rather, it is often expected that the most valuable and longlasting learning outcomes from a physics course will be a repertoire of problem-solving strategies, a familiarity with mathematizing real-world situations, and the development of a strong set of qualitative inferential reasoning skills.

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Using Question Variations To Access Alternate Student Thinking About The Same Physical Situations, Jeffrey Mathis Hawkins

Electronic Theses and Dissertations

Assessing students’ understanding of physics is a critical element for improving physics education. This dissertation presents and demonstrates a method to better assess student understanding of physics by varying the types of questions asked of students. The method presented herein, which is based on the Specific Difficulties and Resources frameworks, involves modifying the task students are asked to complete when analyzing the physics of a particular physical situation. Creating question variations that ask students to address a particular correct or incorrect outcome of the physical situation, eliminate an incorrect outcome, or justify a correct outcome provided to them can provide …

450degree C Aln Thin Film Growth On Nitrided C-Plane Sapphire Substrates, Roger Eastman Feeley

Electronic Theses and Dissertations

Low temperature (LT) growth of strongly textured AlN by molecular beam epitaxy (MBE) has not been extensively investigated. The low mobility of Al adatoms provides a challenge for growth of AlN at low temperatures (<600 >°C). Consequently, AlN growth by MBE is typically at temperatures >700 °C. Growth at these temperatures can limit the selection of substrates and materials to grow with the AlN. Highly oriented, LT AlN thin films (<50 >nm) were grown on c-­‐plane sapphire, using an interrupted growth procedure. Films were grown by periodically interrupting the Al flux with a nitridation. This two-­‐step cycle was repeated until …

Light Matter Interaction In Single Molecule Magnets, Rebecca Cebulka

Electronic Theses and Dissertations

This dissertation includes a series of experimental realizations which focus on studying the coupling between photons and single-molecule magnets (SMMs) in both the weak and strong coupling regimes. In the weak coupling regime, the aim is to achieve coherent control over the time evolution of the spin of SMMs while applying rapid microwave pulses at sub-Kelvin temperatures, where polarization of the spin bath may be achieved without large magnetic fields, allowing the suppression of dipolar dephasing. The continuing results of this experiment will be to provide a window into fundamental sources of decoherence in single-crystal SMMs in an energy range …

A Theoretical Investigation Of Small Organic Molecules On Transition Metal Surfaces, Walter Malone

Electronic Theses and Dissertations

With the ever growing number of proposed desnity functional theory (DFT) functionals it becomes necessary to thoroughly screen any new method to determine its merit. Especially relevant methods include a proper description of the van der Waals (vdW) interaction, which can prove vital to a correct description of a myriad of systems of technological importance. The first part of this dissertation explores the utility of several vdW-inclusive DFT functionals including optB86b-vdW, optB88-vdW, optPBE-vdW, revPBE-vdW, rPW86-vdW2, and SCAN+rVV10 by applying them to model systems of small organic molecules, pyridine and thiophene, on transition metal surfaces. Overall, we find the optB88-vdW functional …

2d Materials Based Heterostructures : A Lithography Free Method., Adel Alruqi

Electronic Theses and Dissertations

Many properties of Two-dimensional (2D) materials are vastly different from those of their 3D counterparts. A large family of 2D materials ranging from gapless graphene to metallic NbSe2 (also superconducting), semiconducting MoS2, and insulating hexagonal boron nitride (h-BN) possessing a broad range of exciting new properties have emerged in recent years. Moreover, 2D materials provide the perfect platform to create laterally and vertically stacked heterostructures with intriguing properties. The physics of 2D materials based heterostructures is extremely interesting and novel 2D-heterostructured devices including tunneling diodes, tunneling transistors, photovoltaic cells, and light-emitting diodes have started to emerge. In this work, we …

Lithium Molybdate-Sulfur Battery., Ruchira Ravinath Dharmasena

Electronic Theses and Dissertations

Rechargeable energy storage systems play a vital role in today’s automobile industry with the emergence of electric vehicles (EVs). In order to meet the targets set by the department of energy (DOE), there is an immediate need of new battery chemistries with higher energy density than the current Li- ion technology. Lithium–sulfur (Li–S) batteries have attracted enormous attention in the energy-storage, due to their high specific energy density of 2600 Wh kg^-1 and operational voltage of 2.0 V. Despite the promising electrochemical characteristics, Li-S batteries suffer from serious technical challenges such as dissolution of polysulfides Li₂S_{x …}

Chemistry And Dissipation At Mineral Surfaces In The Space Environment, William Tucker

Electronic Theses and Dissertations

The composition and morphology of mineral surfaces is known to play an important role in various phenomena relevant to planetary science. For example, the synthesis and processing of complex organics likely occurs at mineral surfaces strongly affected by the space environment. Furthermore, the dissipative and adhesive properties of dust grains may depend strongly on the chemical state of the surface including the presence of dangling bonds, adsorbates, and radicals. In this dissertation, experimental results are first presented which demonstrate that mineral grains subjected to high temperatures in a reducing environment lead to iron nanoparticles which are strongly catalytic for the …

A Study On Radiative Pion Capture As A Source Of Background In The Search For Muon To Electron Conversion At The Mu2e Experiment., Joseph Leibson

Electronic Theses and Dissertations

The following thesis will cover the process of radiative pion capture in the Mu2e experiment at Fermi National Accelerator Laboratory. Radiative pion capture (RPC) is a process that is able to mimic the signal of an electron spawned from the neutrino-less conversion of a muon. In this paper we will discuss the current Standard Model accepted by physicists, and discuss charged lepton flavor violation, which is the motivation behind Mu2e. This paper will cover the theory behind Mu2e and RPC, as well as the apparatus involved in the Mu2e experiment. Next, software and simulations used to carry out the RPC …

High Performance Liquid Crystal Devices For Augmented Reality And Virtual Reality, Md Javed Rouf Talukder

Electronic Theses and Dissertations

See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, …

Processing Of Advanced Infrared Materials, Daniel Mcgill

Electronic Theses and Dissertations

Infrared transparent glassy and crystalline materials often have unique and complex processing requirements but are an important class of materials for such applications as optical windows, lenses, waveplates, polarizers and beam splitters. This thesis investigates two specific materials, one amorphous and one crystalline, that are candidates for use in the short and midwave-infrared and mid and longwave infrared, respectively. It is demonstrated that an innovative uniaxial sintering process, which uses a sacrificial pressure-transmitting medium, can be used to fully densify a 70TeO2-20WO3-10La2O3 (TWL) glass powder. The characteristics of the sintered TWL glass is compared to that of a parent glass …

Nanoscale Functional Imaging By Tailoring Light-Matter Interaction To Explore Organic And Biological Systems, Negar Otrooshi

Electronic Theses and Dissertations

Probing molecular systems with light has been critical to deepen our understanding of life sciences. However, conventional analytical methods fail to resolve small quantities of molecules or the heterogeneity in molecules assembled into complex systems. This bottleneck is mostly attributed to light diffraction limit. In recent years, the successful implementation of new approaches to achieve sub-wavelength chemical speciation with an Atomic Force Microscope (AFM) has paved the way to a deeper understanding of the effect of local composition and structure on the functional properties of a larger scale system. The combination of infrared light, to excite the vibrational modes of …

Asteroid Surfaces: The Importance Of Cohesive Forces, Keanna Jardine

Electronic Theses and Dissertations

Adhesive forces play a significant role on airless bodies due to their weak gravities. Investigating adhesion at the surface of asteroids and their constituent components is vital to understanding their formation and evolution. Previous research has been done to understand the interaction of micron-sized spheres to planar surfaces and sphere-to-sphere interactions, which have been used to develop models of asteroid surfaces. Our investigation experimentally investigates adhesion through atomic force microscopy (AFM) measurements between JSC-1 simulant particles and several AFM tips, including a typical pyramidal gold tip and microspheres of sizes 2 μm and 15 μm. The samples of JSC-1 consist …

Broadband Mid-Infrared Frequency Combs Generated Via Frequency Division, Qitian Ru

Electronic Theses and Dissertations

Frequency combs have revolutionized metrology and demonstrated numerous applications in science and technology. Combs operating in the mid-infrared region could be beneficial for molecular spectroscopy for several reasons. First, numerous molecules have their spectroscopic signatures in this region. Furthermore, the atmospheric window (3-5μm and 8-14μm) is located here. Additionally, a mid-infrared frequency comb could be employed as a diagnostic tool for the many components of human breath, as well as for detection of harmful gases and contaminants in the atmosphere. In this thesis, I used synchronously pumped subharmonic optical parametric oscillators (OPOs) operating at degeneracy to produce ultra-broadband outputs near …

A Study Of Several Applications Of Parallel Computing In The Sciences Using Petsc, Nicholas Stegmeier

Electronic Theses and Dissertations

The importance of computing in the natural sciences continues to grow as scientists strive to analyze complex phenomena. The dynamics of turbulence, astrophysics simulations, and climate change are just a few examples where computing is critical. These problems are computationally intractable on all computing platforms except supercomputers, necessitating the continued development of efficient algorithms and methodologies in parallel computing. This thesis investigates the use of parallel computing and mathematical modeling in the natural sciences through several applications, namely computational fluid dynamics for impinging jets in mechanical engineering, simulation of biofilms in an aqueous environment in mathematical biology, and the solution …

Holographic Optical Elements For Visible Light Applications In Photo-Thermo-Refractive Glass, Fedor Kompan

Electronic Theses and Dissertations

This dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation. The first method involves modification of the original PTR glass rendering it photosensitive to radiation in the visible spectral region and, thus, making possible the recording of holograms in PTR …

Imaging Through Glass-Air Anderson Localizing Optical Fiber, Jian Zhao

Electronic Theses and Dissertations

The fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be insensitive to environmental perturbations, such as mechanical bending or temperature variations. Besides, both coherent and incoherent light sources should be compatible with the …

Fundamental Properties Of Metallic Nanolasers, William Hayenga

Electronic Theses and Dissertations

The last two decades have witnessed tremendous advancements in the area of nanophotonics and plasmonics, which has helped propel the development of integrated photonic sources. Of central importance to such circuits is compact, scalable, low threshold, and efficient coherent sources that can be driven at high modulation frequencies. In this regard, metallic nanolasers offer a unique platform. Their introduction has enabled confinement of light at a subwavelength scale and the ultra-small size of the modes afforded by these structures allows for cavity enhancing effects that can help facilitate thresholdless lasing and large direct modulation bandwidths. In this report, I present …

The Relativistic Harmonic Oscillator And The Generalization Of Lewis' Invariant, Daniel Reinhart

Electronic Theses and Dissertations

In this thesis, we determine an asymptotic solution for the one dimensional relativistic harmonic oscillator using multiple scale analysis and relate the resulting invariant to Lewis' invariant. We then generalize the equations leading to Lewis' invariant so they are relativistically correct. Next we attempt to find an asymptotic solution for the general equations by making simplifying assumptions on the parameter characterizing the adiabatic nature of the system. The first term in the series for Lewis' invariant corresponds to the adiabatic invariant for systems whose frequency varies slowly. For the relativistic case we find a new conserved quantity and seek to …

Catalytic Properties Of Defect-Laden 2d Material From First-Principles, Tao Jiang

Electronic Theses and Dissertations

Two dimensional (2D) materials offer excellent opportunities for application as catalysts for energy needs. Their catalytic activity depends on the nature of defects, their geometry and their electronic structure. It thus important that the characteristics of defect-laden 2D materials be understood at the microscopic level. My dissertation focuses on theoretical and computational studies of several novel nanoscale materials using state-of-the-art techniques based on density functional theory (DFT) with the objective of understanding the microscopic factors that control material functionality. My work has helped establish defect-laden hexagonal boron nitride (dh-BN) as a promising metal-free catalyst for CO2 hydrogenation. Firstly, I showed …

Hybrid Integration Of Second- And Third-Order Highly Nonlinear Waveguides On Silicon Substrates, Guillermo Fernando Camacho Gonzalez

Electronic Theses and Dissertations

In order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film lithium niobate waveguides for highly efficient second-harmonic generation. Through the pursuit of hybrid integration of the two types of waveguides for applications such as on-chip self-referenced optical frequency combs, we have experimentally demonstrated fabrication integrability of …

Third-Order Optical Nonlinearities For Integrated Microwave Photonics Applications, Marcin Malinowski

Electronic Theses and Dissertations

The field of integrated photonics aims at compressing large and environmentally-sensitive optical systems to micron-sized circuits that can be mass-produced through existing semiconductor fabrication facilities. The integration of optical components on single chips is pivotal to the realization of miniature systems with high degree of complexity. Such novel photonic chips find abundant applications in optical communication, spectroscopy and signal processing. This work concentrates on harnessing nonlinear phenomena to this avail. The first part of this dissertation discusses, both from component and system level, the development of a frequency comb source with a semiconductor mode-locked laser at its heart. New nonlinear …

Non-Hermitian And Space-Time Mode Management, Nicholas Nye

Electronic Theses and Dissertations

In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. On the other hand, PT symmetry has emerged from quantum mechanics, when a new class of non-Hermitian Hamiltonian quantum systems was shown to have real eigenvalues. In this work, we demonstrate how PT-symmetric diffractive structures are capable of eliminating diffraction orders in specific directions, while maintaining/enhancing the remaining orders. In the second part of this work, we emphasize on supersymmetry (SUSY) and its applications in …

Multidimensional Spectroscopy Of Mixed-Cation Perovskite Thin Films, Geoffrey Michael Diederich

Electronic Theses and Dissertations

Metal halide perovskite (MHP) thin films are currently undergoing an intense re- search thrust due to the excellent performance of MHP based photovoltaic (PV) devices, which have the potential to revolutionize the worlds energy production via a unique combination of low-cost fabrication and high power conversion efficiency (PCE). However, the vast majority of research is currently aimed at incremental improvements in device PCE, resulting in a body of work without the foundational understanding of the charge-carrier dynamics of the system upon photoexcitation.

This thesis begins with the development of a phase-modulated multidimensional coherent spectroscopy (PM-MDCS) experiment. PM-MDCS is an ultrafast …

Quantitative Aspects Of Interface Remodeling During Germband Extension, Timothy E. Vanderleest

Electronic Theses and Dissertations

Oriented cell intercalation is an essential developmental process that shapes tissue morphologies through the directional insertion of cells between their neighbors. Intercalary behaviors in the early Drosophila embryo occur through a remodeling of cell topologies, with cells contracting shared AP interfaces to a single point, followed by newly juxtaposed DV cells constructing horizontally-oriented interfaces between them. Previous research has focused on properties of cell-cell interfaces, and led to a model in which actomyosin networks mediate higher line tensions at AP interfaces to direct contraction. However, the contribution of tricellular vertices to tissue elongation remains unclear. This study shows that cell …

Nanoscale Thermal Transport In Thermally Isolated Nanostructures, Brian G. Green

Electronic Theses and Dissertations

Experiments with nanoscale structures, designed to measure some of their thermal and optical properties, are the subjects of this dissertation. We studied the transport of thermal energy in systems of nanoparticles, and used the method of transient thermoreflectance to monitor those dynamics, and assess whether thermal transport features special to nanoscale systems emerged. This same method was also used to study the thermal transport of a single system of layered membranes. Optical properties were investigated using computational simulations of a nanoparticle system, using the method of finite-difference time-domain simulation.

In nanoparticle studies, there are two features of interest special to …

Geographic Variations Of Sound Channel Axis In The Global Ocean, Mukunda Kumar Acharya

Electronic Theses and Dissertations

Sound signals are used for imaging and communication in the ocean. Underwater sound speed has a minimum at a certain depth that forms a sound channel for long-range underwater sound propagation. The geographic variation of sound channel is crucial in uses of underwater sound in various environments including ocean acoustic tomography and monitoring of global warming. In this work, sound speed and depth of the channel axis in the global ocean are characterized for their variation with the latitude, longitude, and depth.

Gravitational Radiation From Superradiant Instabilities Of Rotating Black Holes, Shrobana Ghosh

Electronic Theses and Dissertations

We use the Teukolsky formalism to calculate the gravitational radiation from a non-axi\-symmetric cloud formed due to superradiant amplification of a spin-0 bosonic field. We focus on the prospects of the future space-based gravitational wave detector, Laser Interferometer Space Antenna (LISA), and the current version of ground-based detector, Advanced Laser Interferometer Gravitational-Wave Observatory (AdLIGO), to detect or constrain scalars with mass in the range $m_s\in [10^{-19},10^{-15}]$ eV and $m_s\in[10^{-14},10^{-11}]$ eV, respectively. Using astrophysical models of black hole populations calibrated to observations we find that, in optimistic scenarios, AdLIGO could detect up to $10^4$ resolvable events in a four-year search if …

Manifoldlike Causal Sets, Miremad Aghili

Electronic Theses and Dissertations

The content of this dissertation is written in a way to answer the important question of manifold likeness of causal sets. This problem has importance in the sense that in the continuum limit and in the case one finds a formalism for the sum over histories, the result requires to be embeddable in a manifold to be able to reproduce General Relativity. In what follows I will use the distribution of path length in a causal set to assign a measure for manifold likeness of causal sets to eliminate the dominance of nonmanifold like causal sets. The distribution of interval …

Computational Imaging Systems For High-Speed, Adaptive Sensing Applications, Yangyang Sun

Electronic Theses and Dissertations

Driven by the advances in signal processing and ubiquitous availability of high-speed low-cost computing resources over the past decade, computational imaging has seen the growing interest. Improvements on spatial, temporal, and spectral resolutions have been made with novel designs of imaging systems and optimization methods. However, there are two limitations in computational imaging. 1), Computational imaging requires full knowledge and representation of the imaging system called the forward model to reconstruct the object of interest. This limits the applications in the systems with a parameterized unknown forward model such as range imaging systems. 2), the regularization in the optimization process …