Other Physics Commons^™

Implicit-Explicit Higher-Order Time Integration Schemes For Computations Of Structural Dynamics With Fluid-Structure Interaction, José C. Pedro, Mapundi K. Banda, Precious Sibanda

Applications and Applied Mathematics: An International Journal (AAM)

In this paper higher order implicit Runge-Kutta schemes are applied to fluid-structure interaction (FSI) simulations. A staggered approach with a structural predictor is applied to an FSI problem. The equations governing the dynamics of the structure are integrated in time by the Explicit Single Diagonal Implicit Runge-Kutta (ESDIRK) schemes and the arbitrary high order finite volume scheme is taken as the fluid solver. The performance of the ESDIRK scheme of order of convergence three to five is tested. Comparative studies with other time integration schemes which have been successfully applied to FSI problems are undertaken. Comparisons to test the performance …

Free Convective Chemically Absorption Fluid Past An Impulsively Accelerated Plate With Thermal Radiation Variable Wall Temperature And Concentrations, Sanjib Sengupta

Applications and Applied Mathematics: An International Journal (AAM)

The present paper deals with the theoretical study of thermal radiation and chemical reaction on free convective heat and mass transfer flow of a Newtonian viscous incompressible fluid past a suddenly accelerated semi–infinite vertical permeable plate immersed in Darcian absorption media. The fluid media is considered as optically thick and the Rosselend radiative heat flux model is incorporated in the energy equation. The governing equation of motions are first non-dimensionalised and then transformed into a set of ordinary differential equations by employing a suitable periodic transformation. The closed form of the expression for velocity, temperature and concentration fields as well …

Saddle Force Mapping, Molly Totten

Physics

In horseback riding, the size and shape of a saddle can drastically effect the comfort, attitude and performance of the horse as well as the effectiveness of the rider. In an effort to create an accurate means of fitting the saddle to the horse, I have created a pressure sensing device that maps the force differences along critical areas of the horse's back during motion. Using an Arduino microprocessor and appropriate circuits, data was collected about the pressure levels between the saddle and the horse's back and a graphic representation of the findings was created.

Characterizing Alma For Solar Observation, Yi Chai

Theses

ALMA (Atacama Large Millimeter/submillimeter Array) is an antenna array of 66 antennas located in northern Chile at 5000 meters altitude. It is the largest ground-based array operated at millimeter/submillimeter wavelengths. In this thesis, the advantages of using ALMA for solar observation are presented, together with the introduction of a campaign to commission ALMA for solar observations. Observation modes of the solar campaign are reviewed in Chapter 2. Methods for constructing images from single dish data as well as the procedure for processing interferometer data, including calibration and imaging, are given in Chapter 3. The CLEAN algorithm that is used for …

Bicrystallography In Two Dimensions: A Graphical Procedure And Comparison Of Its Results To Experiments, Andrew M. Maas, Peter Moeck

Student Research Symposium

Three dimensional (3D) bicrystallography describes ideal structures of grain boundaries comprehensively at the atomic level as a function of the five macroscopic and two of the four microscopic parameters [1,2]. Free energy minimization of these structures leads to the real structure of these topologically distinct regions within crystals. These minimizations may either reduce the symmetries of ideal bicrystals or leave them intact. Since the symmetries of physical properties need to be compatible (by the Shubnikov-Curie and Curie-Minnigerode-Neumann principles [3]) with the symmetries of the atomic arrangements from which they arise, bicrystallography allows for predictions about which phenomena can occur in …

Thermoelectric Properties Of Nano-Meso-Micro Β-Mno2 Powders As A Function Of Electrical Resistance: Experiment And Theory, Morgan Hedden

Senior Honors Projects, 2010-2019

In this work, the thermoelectric properties of Beta-MnO² powders as a function of electrical resistance are measured and compared to theoretical models. The discovery of a giant Seebeck coefficient by Song et al. in these powders rejuvenated interest in understanding the physical mechanism behind it. A simple pestle and mortar method was used to modify the MnO² powder sizes. We and the largest S coefficient, power factor, and thermal conductivity values were found to be S=-316 uV/K, (sigma)S² =5.8x10^-7 W/mK² and k=0.2096 W/(mK), all observed at a particle electrical resistance of R=9.8 Ohms. From these …

Characterization Of Low Density Intracranial Lesions Using Dual-Energy Computed To Mography, Jessica L. Nute

Dissertations and Theses (Open Access)

Calcific and hemorrhagic foci of susceptibility are frequently encountered on routine brain MR studies. Both etiologies cause variations in local magnetic field strength, leading to dark regions on the MR images that cannot be classified. Single-energy CT (SECT) can be used to identify lesions with attenuation over 100 HU as calcific, however lesions with lower attenuation cannot be reliably identified. While calcific lesions are unlikely to cause harm, hemorrhagic lesions carry a risk of subsequent intracranial bleeding; as such, identification of hemorrhage is vital in preventing the inappropriate use of anticoagulant medications in patients with hemorrhagic lesions.

Given there currently …

Power-Recycled Weak-Value-Based Metrology, Kevin Lyons, Justin Dressel, Andrew N. Jordan, John C. Howell, Paul G. Kwiat

Mathematics, Physics, and Computer Science Faculty Articles and Research

We improve the precision of the interferometric weak-value-based beam deflection measurement by introducing a power recycling mirror, creating a resonant cavity. This results in all the light exiting to the detector with a large deflection, thus eliminating the inefficiency of the rare postselection. The signal-to-noise ratio of the deflection is itself magnified by the weak value. We discuss ways to realize this proposal, using a transverse beam filter and different cavity designs.

Tailoring Optical Complex Fields With Nano-Metallic Surfaces, Guanghao Rui, Qiwen Zhan

Electro-Optics and Photonics Faculty Publications

Recently there is an increasing interest in complex optical fields with spatially inhomogeneous state of polarizations and optical singularities. Novel effects and phenomena have been predicted and observed for light beams with these unconventional states. Nanostructured metallic thin film offers unique opportunities to generate, manipulate and detect these novel fields. Strong interactions between nano-metallic surfaces and complex optical fields enable the development of highly compact and versatile functional devices and systems. In this review, we first briefly summarize the recent developments in complex optical fields. Various nano-metallic surface designs that can produce and manipulate complex optical fields with tailored characteristics …

Cost-Availability Curves For Hierarchical Implementation Of Residential Energy-Efficiency Measures, Roman Villoria-Siegert, Philip Brodrick, Kevin P. Hallinan, Robert J. Brecha

Physics Faculty Publications

Historical residential electricity data and natural gas consumption data were collected for, respectively, 1,200 and 178 residences in a small town in the USA. These data were merged with local building and weather databases, and energy consumption models were developed for each residence, revealing substantial variation in heating and cooling intensity. After estimating approximate physical building characteristics, energy profiles for each residence were calculated, and savings from adoption of the most cost-effective energy-efficiency measures for each residence were estimated. Effectively, we wish to leverage commonly available data sets to infer characteristics of building envelopes and equipment, without the need for …

Optimization-Free Optical Focal Field Engineering Through Reversing The Radiation Pattern From A Uniform Line Source, Yanzhong Yu, Qiwen Zhan

Electro-Optics and Photonics Faculty Publications

A simple and flexible method is presented for the generation of optical focal field with prescribed characteristics. By reversing the field pattern radiated from a uniform line source, for which the electric current is constant along its extent, situated at the focus of a 4Pi focusing system formed by two confocal high-NA objective lenses, the required illumination distribution at the pupil plane for creating optical focal field with desired properties can be obtained. Numerical example shows that an arbitrary length optical needle with extremely high longitudinal polarization purity and consistent transverse size of ~0.36λ over the entire depth of focus …

An Extremum Principle For Charged Black Holes, Shaker Von Price Funkhouser

Physics

There is a well known static condition that characterizes how two or more charged black holes stay in place: this condition is |qi |=mi , where a black hole (labeled by i) has electric charge qi and mass mi . For nearly half a century, this static condition has eluded a simple physical interpretation, without appealing to forces. I provide the first proof that the static condition, |qi |=mi , corresponds to an extremum of the black holes’ total energy. My approach uses geometry and calculus in the context of general relativity. For the non-specialist, this work draws upon one’s …

Tunable Narrow Band Difference Frequency Thz Wave Generation In Dast Via Dual Seed Ppln Opg, Brian Dolasinski, Peter E. Powers, Joseph W. Haus, Adam Cooney

Electro-Optics and Photonics Faculty Publications

We report a widely tunable narrowband terahertz (THz) source via difference frequency generation (DFG). A narrowband THz source uses the output of dual seeded periodically poled lithium niobate (PPLN) optical parametric generators (OPG) combined in the nonlinear crystal 4-dimthylamino-N-methyl-4-stilbazolium-tosylate (DAST). We demonstrate a seamlessly tunable THZ output that tunes from 1.5 THz to 27 THz with a minimum bandwidth of 3.1 GHz. The effects of dispersive phase matching, two-photon absorption, and polarization were examined and compared to a power emission model that consisted of the current accepted parameters of DAST.

Mueller Matrix Spectroscopic Ellipsometry Of Multiferroics, Roman Basistyy

Dissertations

Multiferroics, materials which possess several ferroic orders, are the focus of research in recent years. Among these materials are oxide crystals, such as, for example, RMnO₃, RMn₂O₅, R₃Fe₅O₁₂, where R stands for rare earth ions. The most fascinating physics occurs when magnon-lattice coupling reveals itself in the far-IR spectra of multiferroics. The expected optical behavior puts multiferroics into a more general category of bi-anisotropic materials, the properties of which could be only described using anisotropic dielectric ε(ω), magnetic μ(ω), and …

Electronic, Thermoelectric And Optical Properties Of Vanadium Oxides: Vo2, V2o3 And V2o5, Chiranjivi Lamsal

Dissertations

Correlated electrons in vanadium oxides are responsible for their extreme sensitivity to external stimuli such as pressure, temperature or doping. As a result, several vanadium oxides undergo insulator-to-metal phase transition (IMT) accompanied by structural change. Unlike vanadium pentoxide (V₃O₃), vanadium dioxide (VO₃) and vanadium sesquioxide (V₃O₃) show I MT in their bulk phases. In this study, we have performed one electron Kohn-Sham electronic band-structure calculations of VO₃, V₃O₃ and V₂O₅ in both metallic and insulating phases, implementing a full ab-initio simulation package …

A Comprehensive Study Of Evolution Of Photospheric Magnetic Field And Flows Associated With Solar Eruptions, Shuo Wang

Dissertations

The rapid, irreversible change of the photospheric magnetic field has been recognized as an important element of the solar flare process. Recent theoretical work has shown that such a change would imply Lorentz force perturbations acting on both the outer solar atmosphere and the solar surface. This research uses vector magnetograms obtained with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory to study a number of flares, which range from GOES-class C4 to X5 and occur in four active regions. In all the events, a permanent and rapid change of photospheric magnetic field closely associated with the …

Four Tails Problems For Dynamical Collapse Theories, Kelvin J. Mcqueen

Philosophy Faculty Articles and Research

The primary quantum mechanical equation of motion entails that measurements typically do not have determinate outcomes, but result in superpositions of all possible outcomes. Dynamical collapse theories (e.g. GRW) supplement this equation with a stochastic Gaussian collapse function, intended to collapse the superposition of outcomes into one outcome. But the Gaussian collapses are imperfect in a way that leaves the superpositions intact. This is the tails problem. There are several ways of making this problem more precise. But many authors dismiss the problem without considering the more severe formulations. Here I distinguish four distinct tails problems. The first (bare tails …

Mass Additivity And A Priori Entailment, Kelvin J. Mcqueen

Philosophy Faculty Articles and Research

The principle of mass additivity states that the mass of a composite object is the sum of the masses of its elementary components. Mass additivity is true in Newtonian mechanics but false in special relativity. Physicists have explained why mass additivity is true in Newtonian mechanics by reducing it to Newton’s microphysical laws. This reductive explanation does not fit well with deducibility theories of reductive explanation such as the modern Nagelian theory of reduction, and the a priori entailment theory of reduction that is prominent in the philosophy of mind. Nonetheless, I argue that a reconstruction of the explanation that …

Role Of Antenna Modes And Field Enhancement In Second Harmonic Generation From Dipole Nanoantennas, Domenico De Ceglia, Maria Antonietta Vincenti, Costantino De Angelis, Andrea Locatelli, Joseph W. Haus, Michael Scalora

Electro-Optics and Photonics Faculty Publications

We study optical second harmonic generation from metallic dipole antennas with narrow gaps. Enhancement of the fundamental-frequency field in the gap region plays a marginal role on conversion efficiency. In the symmetric configuration, i.e., with the gap located at the center of the antenna axis, reducing gap size induces a significant red-shift of the maximum conversion efficiency peak. Either enhancement or inhibition of second-harmonic emission may be observed as gap size is decreased, depending on the antenna mode excited at the harmonic frequency. The second-harmonic signal is extremely sensitive to the asymmetry introduced by gap’s displacements with respect to the …

Impact Of Detector-Element Active-Area Shape And Fill Factor On Image Sampling, Restoration, And Super-Resolution, Russell C. Hardie, Douglas R. Droege, Alexander J. Dapore, Mark E. Greiner

Electrical and Computer Engineering Faculty Publications

In many undersampled imaging systems, spatial integration from the individual detector elements is the dominant component of the system point spread function (PSF). Conventional focal plane arrays (FPAs) utilize square detector elements with a nearly 100% fill factor, where fill factor is defined as the fraction of the detector element area that is active in light detection. A large fill factor is generally considered to be desirable because more photons are collected for a given pitch, and this leads to a higher signal-to-noise-ratio (SNR). However, the large active area works against super-resolution (SR) image restoration by acting as an additional …

Chirally-Sensitive Electron-Molecule Interactions, J. M. Dreiling, Timothy J. Gay

Timothy J. Gay Publications

All molecular forms of life have chemically-specific handedness. However, the origin of these asymmetries is not understood. A possible explanation was suggested by Vester and Ulbricht immediately following the discovery of parity violation in 1957: chiral beta radiation in cosmic rays may have preferentially destroyed one enantiomeric form of various biological precursors. In the experiments reported here, we observed chiral specificity in two electronmolecule interactions: quasi-elastic scattering and dissociative electron attachment. Using lowenergy longitudinally spin-polarized (chiral) electrons as substitutes for beta rays, we found that chiral bromocamphor molecules exhibited both a transmission and dissociative electron attachment rate that depended on …

Deriving The Dyer-Roeder Equation From The Geodesic Deviation Equation Via The Newman-Penrose Null Tetrad, Aly Aly

Undergraduate Review

In this paper we examine the geodesic deviation equation using the Newman-Penrose (N-P) formalism for a flat Friedmann-Lemaitre-Robertson-Walker(FLRW) metric [Carroll,S. (2004), Ryden, B. (2003), Newman Penrose(1962)]. We solved the geodesic deviation equation for angular diameter distance, using the relevant N-P components, and the resulting expression was the Dyer-Roeder equation of cosmology [Ryden, B. (2003)] [Schneider et al.(1992)]. This leads us to believe that we can apply the N-P formalism to a perturbed FLRW metric and find a solvable equation for angular diameter distance [Kling Campbell(2008)]. The perturbed FLRW metric incorporates clumps of matter into a metric that is on average …

Magnetic Force Microscopy Study Of Zr2co11-Based Nanocrystalline Materials: Effect Of Mo Addition, Lanping Yue, Yunlong Jin, Wenyong Zhang, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The addition of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr₂Co₁₁-based nanocrystalline permanent magnets. The effect of Mo addition on magnetic domain structures of melt spun nanocrystalline Zr₁₆Co_84−xMo_x (𝑥 = 0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. The coercivity of the samples increases with the increase in Mo content (𝑥 ≤ 1.5). The maximum energy product (𝐵𝐻)_max increases with increasing 𝑥 from 0.5 MGOe for 𝑥 …

A Collaborative Adaptive Wiener Filter For Multi-Frame Super-Resolution, Khaled M. Mohamed, Russell C. Hardie

Electrical and Computer Engineering Faculty Publications

Factors that can limit the effective resolution of an imaging system may include aliasing from under-sampling, blur from the optics and external factors, and sensor noise. Image restoration and super-resolution (SR) techniques can be used to improve image resolution. One SR method, developed recently, is the adaptive Wiener filter (AWF) SR algorithm. This is a multi-frame SR method that combines registered temporal frames through a joint nonuniform interpolation and restoration process to provide a high-resolution image estimate. Variations of this method have been demonstrated to be effective for multi-frame SR, as well demosaicing RGB and polarimetric imagery. While the AWF …

Phenomenology Of A Toy Model Inspired By The Spontaneous Reduction Of The Spectral Dimension In Quantum Gravity, Patrick A. Greene

Honors Theses and Capstones

Attempts to formulate a quantum theory of gravity have generated many sophisticated models. Though fundamentally different, they necessarily exhibit behaviors resembling experimental observations and standard theoretical expectations. Often, their similarities go no further. However many models unexpectedly predict a change in the spectral dimension of spacetime at very small scales (See [1] and references therein for examples). In particular, some of the models predict the spectral dimension changes from 4 to 2. This paper investigates the phenomenological consequences of a toy model that use Planck-scale 2D hypersurfaces, specifically triangles, embedded in 4D Minkowski spacetime. We randomly generated sequences of triangles …

Black Hole Microstates In String Theory, Joseph Lewkowicz

Legacy Theses & Dissertations (2009 - 2024)

String theory has resolved the information paradox associated with entropy of black holes by identifying microscopic states contributing to this entropy. This thesis reviews the origin of the paradox, and discusses the progress in resolving it, starting from the counting of states by Strominger and Vafa, and culminating in the current work on constructing fuzzball geometries. A particular emphasis is given to a promising technique for constructing new geometries known as spectral flow.

Magnetic Chiral Spin Textures By Imprinting, Robert Streubel, F. Kronast, U. Rössler, O. G. Schmidt, P. Fischer, D. Makarov

Robert Streubel Papers

The unique properties of non-trivial topological states, e.g. magnetic skyrmions [1] may path the way towards novel spintronic devices [2]. However, these spin textures have only been observed in special classes of materials possessing non-centrosymmetric crystal structure [1,3-6] and at low temperatures, which limits their application potential. We offer an alternate route to design synthetic magnetic heterostructures that resemble swirls, vortices or skyrmions with distinct topological charge densities at room temperature. By vertically stacking two magnetic nanopatterns with in-and out-of-plane magnetization and tailoring the interlayer exchange coupling, non-collinear spin textures with tunable topological charge can be imprinted (Fig. 1a).

Mechanical Properties Of Self-Assembled Nanoparticle Membranes: Stretching And Bending, Yifan Wang, Pongsakorn Kanjanaboos, Sean P. Mcbride, Edward Barry, Xiao-Min Lin, Heinrich M. Jaeger

Physics Faculty Research

Monolayers composed of colloidal nanoparticles, with thickness less than ten nanometers, have remarkable mechanical strength and can suspend over micron-sized holes to form free-standing membranes. We discuss experiments probing the tensile strength and bending stiffness of these self-assembled nanoparticle sheets. The fracture behavior of monolayers and multilayers is investigated by attaching them to elastomer substrates which are then stretched. For different applied strain the fracture patterns are imaged down to the scale of single particles. The resulting detailed information about the crack width distribution allows us to relate the measured overall tensile strength to the distribution of local bond strengths …

Question 1: Star Speeds; Question 2: Slurping Gasoline, Larry Weinstein

Physics Faculty Publications

One piece of evidence that the center of our galaxy contains a super-massive black hole came from measuring the speed of a star orbiting that black hole. What is the maximum speed of that star?

If instead of carrying their gas in fuel tanks, cars “slurped up” a stream of gas as they drove, how thick a stream of gas would each car need?

Question 1: "Up" — A Fermi Question About Buoyancy; Question 2: Traffic Jams, Larry Weinstein

Physics Faculty Publications

Is it possible for a house to fly by the uplift of balloons, like in the movie "Up"? (written by R. Allart, A. Cazenave, and A. Müller, University of Geneva)

How much total time do Americans spend waiting in traffic each year? What is the total cost of this time?