Physics Commons^™

Passive Planar Terahertz Retroreflectors, Dhruvkumar Desai

Theses

As the application of the Terahertz (THz) band (0.1 - 10 THz) is investigated in various settings, wireless communication stands out as an important frontier to explore. The benefits of increased bandwidth and data rates it promises will only be realized if new technology is developed to support it. Specifically, since THz wireless communication links are typically line-of-sight (LoS), the LoS can be blocked by moving obstacles, thereby requiring alternative link paths. One proposed solution for indoor wireless communications involves systems of steerable antennas, reflective "wallpaper", and steerable mirrors which would redirect THz beams around a blocking obstacle.

As an …

Black Hole Microstates & Integrable Deformation In String Theory, Jia Tian

Legacy Theses & Dissertations (2009 - 2024)

In this thesis, we study microstate geometries of black holes in string theory and explore several aspects of integrabile Conformal Field Theories (CFTs).

The Entropic Dynamics Approach To The Paradigmatic Quantum Mechanical Phenomena, Susan Difranzo

Legacy Theses & Dissertations (2009 - 2024)

Standard Quantum Mechanics, although successful in terms of calculating and predicting

The Inferential Design Of Entropy And Its Application To Quantum Measurements, Kevin Vanslette

Legacy Theses & Dissertations (2009 - 2024)

This thesis synthesizes probability and entropic inference with Quantum Mechanics and quantum measurement [1-6]. It is shown that the standard and quantum relative entropies are tools \emph{designed} for the purpose of updating probability distributions and density matrices, respectively [1]. The derivation of the standard and quantum relative entropy are completed in tandem following the same inferential principles and design criteria. This provides the first design derivation of the quantum relative entropy while also reducing the number of required design criteria to two.

Evaluating The Effectiveness Of Current Atmospheric Refraction Models In Predicting Sunrise And Sunset Times, Teresa Wilson

Dissertations, Master's Theses and Master's Reports

The standard value for atmospheric refraction on the horizon of 34', used in all publicly available sunrise and sunset calculators, is found to be inadequate. The assumptions behind atmospheric models that predict this value fail to account for real meteorological conditions. The result is an uncertainty of one to five minutes in sunrise and sunset predictions at mid-latitudes (0° - 55° N/S). A sunrise/set calculator that interchanges the refraction component by varying the refraction model was developed. Two atmospheric refraction models of increasing complexity were tested along with the standard value. The predictions were compared with data sets of observed …

Geodesic Structure In Schwarzschild Geometry With Extensions In Higher Dimensional Spacetimes, Ian M. Newsome

Theses and Dissertations

From Birkoff's theorem, the geometry in four spacetime dimensions outside a spherically symmetric and static, gravitating source must be given by the Schwarzschild metric. This metric therefore satisfies the Einstein vacuum equations. If the mass which gives rise to the Schwarzschild spacetime geometry is concentrated within a radius of r=2M, a black hole will form. Non-accelerating particles (freely falling) traveling through this geometry will do so along parametrized curves called geodesics, which are curved space generalizations of straight paths. These geodesics can be found by solving the geodesic equation. In this thesis, the geodesic structure in the Schwarzschild geometry …

Kinetic Monte Carlo Simulation Of Binary Alloys, Timothy Craig Marshall

Theses and Dissertations

There are many tools to simulate physical phenomena. Generally, the simulation technique is defined by the size of the simulation area. Two well know techniques for simulating atom dynamics are kinetic Monte Carlo (kMC) and molecular dynamics (MD). In this work we simulate physical vapor deposition of binary metallic systems using the kMC technique. A sufficient quantity of atoms are deposited so that morphological features can be observed. Where kMC has fallen short we have used MD to supplement our results.

Electrical Properties Of Metal Semiconductor Contacts - Metals On Mos2: A Case Study, Xiao Chang

Theses

Properties of monolayer semiconductor, MoS2, are presented in the research. Schottky barrier height and Schottky-Mott rules are discussed. The current-voltage measurement and capacitance-voltage measurement are analyzed considering the role of the work function. We mainly focus on metal semiconductor contacts on molybdenum disulfide (MoS2). The properties of bulk and monolayer molybdenum disulfide are discussed. The differences between the bulk and monolayer, based on band gap structure theory, are presented. Utilizing the data obtained in the literature, the influence of temperature on the electrical properties of monolayer molybdenum disulfide are analyzed. In particular, the electrical properties of metals on MoS2 such …

Magnetocrystalline Anisotropy Of "-Fe2o3, Imran Ahamed, Rohilt Pathak, Arti Kashyap

Nebraska Center for Materials and Nanoscience: Faculty Publications

The epsilon Fe₂O₃ phase of iron oxide has been studied to understand the spin structure and the magnetocrystalline anisotropy in the bulk and in thin films of "-Fe₂O₃ and Co-doped "-Fe₂O₃. The preferential magnetization direction in the nanoparticles of "-Fe₂O₃ is along the a-axis [M. Gich et al., Chem. Mater. 18, 3889 (2006)]. Compared to the bulk band gap of 1.9 eV, the thin-film band gap is reduced to 1.3 eV in the Co-free films and to 0.7 eV in the film with partial …

Texture Development And Coercivity Enhancement In Cast Alnico 9 Magnets, Wenyong Zhang, Shah Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, Iver Anderson, Matthew Kramer, Wei Tang, Jeff Shield, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The effect of Y addition and magnetic field on texture and magnetic properties of arc-melted alnico 9 magnets has been investigated. Small additions of Y (1.5 wt.%) develop a (200) texture for the arc-melted alnico 9 magnet. Such a texture is hard to form in cast samples. To achieve this goal, we set up a high-field annealing system with a maximum operation temperature of 1250⁰ C. This system enabled annealing in a field of 45 kOe with subsequent draw annealing for the solutionized buttons; we have been able to substantially increase remanence ratio and coercivity, from 0.70 and 1200 …

Underwater Acoustic Signal Analysis Toolkit, Kirk Bienvenu Jr

University of New Orleans Theses and Dissertations

This project started early in the summer of 2016 when it became evident there was a need for an effective and efficient signal analysis toolkit for the Littoral Acoustic Demonstration Center Gulf Ecological Monitoring and Modeling (LADC-GEMM) Research Consortium. LADC-GEMM collected underwater acoustic data in the northern Gulf of Mexico during the summer of 2015 using Environmental Acoustic Recording Systems (EARS) buoys. Much of the visualization of data was handled through short scripts and executed through terminal commands, each time requiring the data to be loaded into memory and parameters to be fed through arguments. The vision was to develop …

System Characterizations And Optimized Reconstruction Methods For Novel X-Ray Imaging, Huifeng Guan

McKelvey School of Engineering Theses & Dissertations

In the past decade there have been many new emerging X-ray based imaging technologies developed for different diagnostic purposes or imaging tasks. However, there exist one or more specific problems that prevent them from being effectively or efficiently employed. In this dissertation, four different novel X-ray based imaging technologies are discussed, including propagation-based phase-contrast (PB-XPC) tomosynthesis, differential X-ray phase-contrast tomography (D-XPCT), projection-based dual-energy computed radiography (DECR), and tetrahedron beam computed tomography (TBCT). System characteristics are analyzed or optimized reconstruction methods are proposed for these imaging modalities. In the first part, we investigated the unique properties of propagation-based phase-contrast imaging technique …

System Optimization And Iterative Image Reconstruction In Photoacoustic Computed Tomography For Breast Imaging, Yang Lou

McKelvey School of Engineering Theses & Dissertations

Photoacoustic computed tomography(PACT), also known as optoacoustic tomography (OAT), is an emerging imaging technique that has developed rapidly in recent years. The combination of the high optical contrast and the high acoustic resolution of this hybrid imaging technique makes it a promising candidate for human breast imaging, where conventional imaging techniques including X-ray mammography, B-mode ultrasound, and MRI suffer from low contrast, low specificity for certain breast types, and additional risks related to ionizing radiation. Though significant works have been done to push the frontier of PACT breast imaging, it is still challenging to successfully build a PACT breast imaging …

Flow Anisotropy Due To Thread-Like Nanoparticle Agglomerations In Dilute Ferrofluids, Alexander Cali, Wah-Keat Lee, A. David Trubatch, Philip Yecko

Department of Applied Mathematics and Statistics Faculty Scholarship and Creative Works

Improved knowledge of the magnetic field dependent flow properties of nanoparticle-based magnetic fluids is critical to the design of biomedical applications, including drug delivery and cell sorting. To probe the rheology of ferrofluid on a sub-millimeter scale, we examine the paths of 550 μm diameter glass spheres falling due to gravity in dilute ferrofluid, imposing a uniform magnetic field at an angle with respect to the vertical. Visualization of the spheres’ trajectories is achieved using high resolution X-ray phase-contrast imaging, allowing measurement of a terminal velocity while simultaneously revealing the formation of an array of long thread-like accumulations of magnetic …

Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough

Doctoral Dissertations

Diamond films are used at the Spallation Neutron Source (SNS) as the primary charge exchange foils (i.e., stripper foils) of the accelerated 1 GeV (Gigaelectron volts) hydride ions. The most common type of film used is a nanocrystalline diamond film, typically 17 mm x 45 mm (millimeter) with an aerial density of 350 μg/cm² (microgram per square centimeter). The diamond film is deposited on a corrugated silicon substrate using plasma-assisted chemical vapor deposition. After the growth of the diamond film, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon handle that …

Fractional Order Thermoelastic Deflection In A Thin Circular Plate, J. J. Tripathi, S. D. Warbhe, K. C. Deshmukh, J. Verma

Applications and Applied Mathematics: An International Journal (AAM)

In this work, a quasi-static uncoupled theory of thermoelasticity based on time fractional heat conduction equation is used to model a thin circular plate, whose lower surface is maintained at zero temperature whereas the upper surface is insulated. The edge of the circular plate is fixed and clamped. Integral transform technique is used to derive the analytical solutions in the physi-cal domain. The numerical results for temperature distributions and thermal deflection are com-puted and represented graphically for Copper material.

Qualitative Results On Mixed Problem Of Micropolar Bodies With Microtemperatures, Marin Marin, Lavinia Codarcea, Adina Chirila

Applications and Applied Mathematics: An International Journal (AAM)

The aim of our study is to transform the mixed initial boundary value problem considered in the context of micropolar thermoelastic bodies whose micro-particles possess microtemperatures in a temporal evolutionary equation on a Hilbert space. Then, with the help of some results from the theory of semigroups, the existence and the uniqueness of the solution for this equation is proved. Finally, we approach the continuous dependence of the solution upon initial data and loads, also with the help of the semigroup.

Thermoelastic Analysis Of A Nonhomogeneous Hollow Cylinder With Internal Heat Generation, V. R. Manthena, N. K. Lamba, G. D. Kedar

Applications and Applied Mathematics: An International Journal (AAM)

In the present paper, we have determined the heat conduction and thermal stresses of a hollow cylinder with inhomogeneous material properties and internal heat generation. All the material properties except Poisson’s ratio and density are assumed to be given by a simple power law in axial direction. We have obtained the solution of the two dimensional heat conduction equation in the transient state in terms of Bessel’s and trigonometric functions. The influence of inhomogeneity on the thermal and mechanical behavior is examined. Numerical computations are carried out for both homogeneous and nonhomogeneous cylinders and are represented graphically.

Applications Of Planar Newtonian Four-Body Problem To The Central Configurations, M. R. Hassan, M. S. Ullah, Md. Aminul Hassan, Umakant Prasad

Applications and Applied Mathematics: An International Journal (AAM)

The present study deals with the applications of the planar Newtonian four-body problem to
the different central configurations. The basic concept of central configuration is that the
vector force must be in the direction of the position vector so that the origin may be taken at
the centre of mass of the four bodies and the force towards the position vector multiplied by
corresponding inverse mass is directly proportional to the position vector relative to the
centre of mass. For applying the Newtonian four body problem to the central configuration,
the equations of motion of four bodies have been established …

Phase Transitions And The Casimir Effect In Neutron Stars, William Patrick Moffitt

Masters Theses

What lies at the core of a neutron star is still a highly debated topic, with both the composition and the physical interactions in question. In this thesis, we made assumptions regarding the composition to further study the interactions of matter during the transition phases. These phases, also known as nuclear pasta, come from the unique physical conditions which occur within neutron stars. We examine the feasibility of the Casimir effect manifesting during these phases, as well as the effects it would have on the total energy of the system. We find that the crust-core transition cannot support the proper …

Energy From Active Galactic Nuclei And The Effects On Host Spiral Galaxies, Amanda Schilling

Graduate Theses and Dissertations

I have investigated the energy output of active galactic nuclei (AGN) in order to understand how these objects evolve and the impact they may have on host galaxies. First, I looked at a sample of 96 AGN at redshifts $z \sim 2, 3,$ and $4$ which have imaging and thus luminosity measurements in the $griz$ and $JHK$ observed wavebands. For these galaxies, I have co-epochal data across those bands which accounted for variability in AGN luminosity. I used the luminosity measurements in the five bands to construct spectral energy distributions (SED) in the emitted optical-UV bands for each AGN. I …

Interactions Of Thermoelastic Beam In Modified Couple Stress Theory, Rajneesh Kumar, Shaloo Devi

Applications and Applied Mathematics: An International Journal (AAM)

This paper is concerned with the study of thermoelastic beam in modified couple stress theory. The governing equations of motion for modified couple stress theory and heat conduction equation for non-Fourier (non-classical process) are investigated to model the vibrations in a homogeneous isotropic thin beam in a closed form by employing the Euler Bernoulli beam theory. The generalized theories of thermoelasticity with one and two relaxation times are used to model the problem. Both ends of the beam are simply supported. The Laplace transform technique applied to solve the system of equations which are written in dimensionless form. A general …

Speckle Effects In Target-In-The-Loop Laser Beam Projection Systems, Mikhail Vorontsov

Electro-Optics and Photonics Faculty Publications

In target-in-the-loop laser beam projection scenarios typical of remote sensing, directed energy, and adaptive optics applications, a transmitted laser beam propagates through an optically inhomogeneous medium toward a target, scatters off the target’s rough surface, and returns back to the transceiver plane. Coherent beam scattering off the randomly rough surface results in strong speckle modulation in the transceiver plane. This speckle modulation has been a long-standing challenge that limits performance of remote sensing, active imaging, and adaptive optics techniques. Using physics-based models of laser beam scattering off a randomly rough surface, we show that received speckle-field spatial and temporal characteristics …

Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, Josiah Sinclair, Matin Hallaji, Aephraim M. Steinberg, Jeff Tollaksen, Andrew N. Jordan

Mathematics, Physics, and Computer Science Faculty Articles and Research

We analytically and numerically investigate the performance of weak-value amplification (WVA) and related parameter estimation methods in the presence of temporally correlated noise. WVA is a special instance of a general measurement strategy that involves sorting data into separate subsets based on the outcome of a second “partitioning” measurement. Using a simplified correlated noise model that can be analyzed exactly together with optimal statistical estimators, we compare WVA to a conventional measurement method. We find that WVA indeed yields a much lower variance of the parameter of interest than the conventional technique does, optimized in the absence of any partitioning …

Analysis Of The Joint Impact Of Atmospheric Turbulence And Refractivity On Laser Beam Propagation, Victor A. Kulikov, Mikhail Vorontsov

Electro-Optics and Photonics Faculty Publications

A laser beam propagation model that accounts for the joint effect of atmospheric turbulence and refractivity is introduced and evaluated through numerical simulations. In the numerical analysis of laser beam propagation, refractive index inhomogeneities along the atmospheric propagation path were represented by a combination of the turbulence-induced random fluctuations described in the framework of classical Kolmogorov turbulence theory and large-scale refractive index variations caused by the presence of an inverse temperature layer. The results demonstrate that an inverse temperature layer located in the vicinity of a laser beam’s propagation path may strongly impact the laser beam statistical characteristics including the …

Proposed Method For Measuring The Let Of Radiotherapeutic Particle Beams, Stephen D. Bello

Physics & Astronomy ETDs

The Bragg peak geometry of the depth dose distributions for hadrons allows for precise and effective dose delivery to tumors while sparing neighboring healthy tissue. Further, compared against other forms of radiotherapeutic treatments, such as electron beam therapy (EBT) or photons (x and \(\gamma\)-rays), hadrons create denser ionization events along the particle track, which induces irreparable damage to DNA, and thus are more effective at inactivating cancerous cells. The measurement of radiation's ability to inactivate cellular reproduction is the relative biological effectiveness (RBE). A quality related to the RBE that is a measurable physical property is the linear energy transfer …

Geothermal Flux And Phreatic Speleogenesis In Gypsum, Halite, And Quartzite Rocks, Giovanni Badino

International Journal of Speleology

The first layers of rock underground are in thermal contact with the external atmosphere mainly through infiltrating meteoric water. This relatively cool zone absorbs rising geothermal energy, which heats the water. If the aquifer consists of gypsum, halite or quartzite, the water at those depths is usually salt-saturated, so the increase in temperature renders the water aggressive again. This in turn leads to rock dissolution and formation of phreatic conduits. This way, the geothermal flow creates caves that do not necessarily reach the surface. This paper analyzes the speed of the excavation, which, in different types of rocks, depends only …

Production Of Cosmological Observables During The Inflationary Epoch, Cody Goolsby-Cole

Doctoral Dissertations

This dissertation proposal explores the production of present day cosmological observables which might have been produced during the inflationary era. The first observable is the current net electric charge of our observable universe produced by charge fluctuations during inflation. Next, we examine the possibility of a signal in the primordial gravitational wave power spectrum produced by a scalar field with a time dependent mass. Finally, we examine primordial magnetic fields produced during inflation through the Ratra model coupling with the Schwinger effect.

Superconductivity At Т≈200 K In Bismuth Cuprates Synthesized Using Solar Energy, J. Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, G. Donadze

Faculty Publications, Chemistry

When investigating low-frequency (0.1 Hz) oscillations of multiphase high-temperature cuprate superconductors (HTCS) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak (ΔT~100 К) with a maximum at Т≈200 К was detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature Т<Тс with subsequent slow warming up to room temperature with invariance of the applied field. The attenuation peak height depended on the preliminaryorientation (before cooling) of the samples θ in the measured permanent magnetic field Н. On the one hand, it is well known that, after the FC procedure and subsequent slow warming up, at the temperatures close to the critical temperature Тс, the attenuation peak associated with “melting” of the Abrikosov frozen vortex structure and its disappearance at Т >Тс is detected in monophase samples. At the same time, in most multiphase bismuth HTCS samples, synthesized using solar energy and superfast quenching of the melt, the attenuation peak with the maximum at Т≈200 К was observed.Depending on the conditions of synthesis, the attenuation peak could …

Calibration Of Temperature Sensors In Preparation For The 2017 Total Solar Eclipse, Erick Agrimson, Kaye Smith, Ana Taylor, Vina Onyango-Robshaw, Rachel Lang, Alynie Xiong, Peace Sinyigaya, Grace Maki, Rachel Dubose, Brittany Craig, James Flaten, Gordon Mcintosh

2017 Academic High Altitude Conference

In preparation for the 2017 total solar eclipse, St. Catherine University developed a calibration protocol for the temperature sensors flown during thermal wake boom experiments. The calibration method used a standard two-point technique that corrected each individual sensor for both slope and offset errors using a high quality NIST certified thermocouple as the temperature standard. Our method is not absolute but corrects each sensor relative to the NIST standard so that we feel some confidence that individual sensor variations are mitigated. In preparation for the eclipse, calibration curves were generated for over 200 individual digital and thermistor temperature sensors.