Digital Commons Network^™

The Design And Construction Of An Out-Of-Plane Sensitive Electronic Speckle Pattern Interferometer For Non-Destructive Testing Applications, Alexander Burden

Masters

There are many non-destructive testing (NDT) techniques use din industry, which employ acoustic emission, ultrasound, X-rays and thermography. Optical interferometric methodology is being increasingly used in industry. Electronic Speckle Pattern Interferometry (ESPI) is one of the principal optical interferometric techniques used in NDT to measure deformations. Optical surface metrology offers many advantages over conventional methods. These include greater sensitivity, improved lateral and vertical resolution, non-contact and full field measurement. Conventional methods of NDT however continue to be chosen over ESPI. The objective of this thesis is focused on making ESPI more feasible as a NDT technique for use in industry. …

Science And Security Watch: A Threat To The United States From Foreign Graduate Students Training In Physics?, Ibpp Editor

International Bulletin of Political Psychology

This article critiques concerns of some United States (US) security analysts that foreign graduate students in physics who train at universities within the US present security vulnerabilities for the US.

A First Principles Warm Inflation Model That Solves The Cosmological Horizon And Flatness Problems, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

A quantum field theory warm inflation model is presented that solves the horizon and flatness problems. The model obtains, from the elementary dynamics of particle physics, cosmological scale factor trajectories that begin in a radiation dominated regime, enter an inflationary regime, and then smoothly exit back into a radiation dominated regime, with non-negligible radiation throughout the evolution.

New Instrumentation For The Detection Of Sulfur Dioxide In The Remote Atmosphere, Dennis Keith Nicks

Chemistry and Biochemistry

Sulfur gases are an important chemical component of the atmosphere. Gaseous sulfur compounds effect the acidity of rainwater and are important precursors to aerosol particles which affect public health, climate and visibility of scenic vistas such as the Grand Canyon. Sulfate aerosols are also known to participate in ozone catalysis in the stratosphere. A vast majority of the gaseous sulfur cycling through the atmosphere will exist as sulfur dioxide (SO2) at some time during its atmospheric lifetime. Since SO 2 is a primary component of the atmospheric sulfur cycle, quality measurements of this gas are important to understanding the cycling …

Modeling Of Arctic Stratus Cloud Formation And The Maintenance Of The Cloudy Arctic Boundary Layer, Qiuqing Zhang

Theses (Unassigned)

The formation of Arctic stratus clouds (ASCs) and the maintenance of the cloudy Arctic boundary layer are studied with two models: a one-dimensional radiative-convective model and a three-dimensional large eddy simulation (LES) model. The one-dimensional radiative-convective model consists of a comprehensive radiative module, a cloud parameterization with detailed microphysics and a convective adjustment scheme. The model is designed specifically for studying ASC formation. With this model, the roles of radiation and cloud microphysics in the formation of ASCs and multiple cloud layers are investigated. The simulations reproduce both single and multiple cloud layers that were observed with inversions of temperature …

Helium And Heavy Ion Measurements With The Crres Satellite., Edmund Gary Clayton

LSU Historical Dissertations and Theses

The CRRES satellite was in service from July 1990 to October 1991, during a period of high solar modulation and solar activity. The ONR-604 experiment aboard CRRES measured helium with isotopic resolution in the energy range 38--110 MeV/nucleon, and heavy ions through iron at 200--500 MeV/nucleon. Although solar modulation was high throughout the CRRES mission, the mission included periods of solar quiescence as well as a number of large solar flares and associated solar energetic particle events. Measurements were made of helium and heavy ions during both the quiet times and the flare periods. A study was made to search …

Atmospheric Transport And Deposition Of Water -Soluble Nitrogen To The Gulf Of Maine, Carolyn Estelle Jordan

Doctoral Dissertations

An intensive sampling program was carried out from May 1994 through November 1997 on the shore of the Gulf of Maine in New Castle, New Hampshire. Daily (24 hour averages) samples of bulk aerosol and gas phase HNO3, precipitation, and 20 aerosol size distributions were obtained. Particulate NH4+ and gas phase HNO3 were the dominant water-soluble nitrogen species in the atmosphere. Nitrate was the dominant inorganic nitrogen ion in precipitation.

These samples were used with 1000 hPa streamlines to classify sampled air masses according to their surface level transport and chemistry. Overall, mixed conditions occurred in 42% of the samples, …

Analyzing Mean Transport Equations Of Turbulence And Linear Disturbances In Decaying Flows, W. D. Thacker, T. B. Gatski, C. E. Grosch

CCPO Publications

The decay of laminar disturbances and turbulence in mean shear-free flows is studied. In laminar flows, such disturbances are linear superpositions of modes governed by the Orr-Sommerfeld equation. In turbulent flows, disturbances are described through transport equations for representative mean quantities. The link between a description based on a deterministic evolution equation and a probability-based mean transport equation is established. Because an uncertainty in initial conditions exists in the laminar as well as the turbulent regime, a probability distribution must be defined even in the laminar case. Using this probability distribution, it is shown that the exponential decay of the …

Multimillion Atom Molecular Dynamics Simulations Of Adhesion And Nanoindentation Of Silicon Nitride., Phillip Judson Walsh

LSU Historical Dissertations and Theses

Multi-million atom molecular dynamics (MD) simulations of nanoindentation of silicon nitride and amorphization and fracture of silicon diselenide nanowires are performed on massively parallel architectures. System sizes range from 75,803 atoms to over 10 million atoms. The process of amorphization and fracture in silicon diselenide nanowires is followed using configuration space images in smaller wires and local stress and temperature calculations in larger wires. A structural transformation in the nanowire cross sections is investigated. The nanowires are found to contract in one direction perpendicular to the applied strain while expanding in the other, so that initially circular nanowires are transformed …

On The Numerical Solution Of The Cylindrical Poisson Equation For Isolated Self -Gravitating Systems., Howard Saul Cohl

LSU Historical Dissertations and Theses

This dissertation addresses the need for an accurate and efficient technique which solves the Poisson equation for arbitrarily complex, isolated, self-gravitating fluid systems. Generally speaking, a potential solver is composed of two distinct pieces: a boundary solver and an interior solver. The boundary solver computes the potential, phi(xB) on a surface which bounds some finite volume of space, V, and contains an isolated mass-density distribution, rho(x). Given rho(x) and phi(xB), the interior solver computes the potential phi(x) everywhere within V. Herein, we describe the development of a numerical technique which efficiently solves Poisson's equation in cylindrical coordinates on massively parallel …

Improving Searches For Gravitational Wave Bursts., Carroll Andrew Morse

LSU Historical Dissertations and Theses

The first half of this dissertation discusses the details of calibrating a resonant mass gravitational wave antenna and determining its sensitivity. We dispense with the assumption of a perfectly tuned antenna and transducer and model the system using a coordinate rotation. We demonstrate that all of the important model parameters can be directly measured. We demonstrate that the signal response of the two detector modes should be equal despite any mistuning and that the mistuning parameter can be measured in two separate ways. These properties are useful for determining the degree to which a real detector's behavior parallels that of …

Insulator-Metal Crossover Near Optimal Doping In Pr22xcexcuo4: Anomalous Normal-State Low Temperature Resistivity, P. Fournier, P. Mohanty, E. Maiser, S. Darzens, T. Venkatesan, C. J. Lobb, G. Czjzek, Richard A. Webb, R. L. Greene

Faculty Publications

Normal-state resistivity measurements at high fields and low temperatures in electron-doped Pr_2-xCe_xCuO₄ thin films reveal an insulator-metal crossover near a doping level x≈0.15, similar to a previous report on hole-doped La_2-xSr_xCuO₄. The temperature dependence of the resistivity of insulatinglike samples is sublogarithmic, while for metallic samples (with x = 0.17) the resistivity is linear from 40 mK to 40 K. This surprising latter observation suggests an unusual contribution to the scattering processes at low temperature in these materials. We conclude that the ground state at x = 0.15, corresponding …

Strong Dissipative Behavior In Quantum Field Theory, Arjun Berera, Marcelo Gleiser, Rudnei O. Ramos

Dartmouth Scholarship

We study the conditions under which an overdamped regime can be attained in the dynamic evolution of a quantum field configuration. Using a real-time formulation of finite temperature field theory, we compute the effective evolution equation of a scalar field configuration, quadratically interacting with a given set of other scalar fields. We then show that, in the overdamped regime, the dissipative kernel in the field equation of motion is closely related to the shear viscosity coefficient, as computed in scalar field theory at finite temperature. The effective dynamics is equivalent to a time-dependent Ginzburg-Landau description of the approach to equilibrium …

Four Paradoxes Involving The Second Law Of Thermodynamics, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

Recently four independent paradoxes have been proposed which appear to challenge the second law of thermodynamics [1-8]. These paradoxes are briefly reviewed. It is shown that each paradox results from a synergism of two broken symmetries - one geometric, one thermodynamic

Studies Of Compositional Variations In The Thermosphere And Ionosphere Using Far-Ultraviolet Images From De-1, Thomas Jerome Immel

Theses (Unassigned)

The Dynamics Explorer mission returned a wealth of information from its two orbiting platforms. Of interest here are the three scanning photometers aboard the high-altitude platform DE-1, which obtained hundreds of thousands of global images of Earth, beginning in September of 1981, while using broad- and narrow-band filters to isolate particular terrestrial emissions. The far-ultraviolet (FUV) emissions include the line emissions of OI (130.4 and 135.6 nm) and the band emissions of $\rm N\sb2$ LBH, the brightness of each yielding information on the composition of the upper atmosphere. The OI emissions are related to the column density of atomic oxygen …

Single And Multiple Electromagnetic Scattering By Size -Shape Distributions Of Small Nonspherical Particles, Frank Michael Schulz

Theses (Unassigned)

A comprehensive model for light scattering by size-shape distributions of randomly oriented nonspherical particles is developed. The model uses spheroids as model particles. The vector Helmholtz equation is solved with a new separation of variables (SVM) approach that allows one to calculate the ensemble-averaged single scattering optical properties of ensembles of randomly oriented particles analytically. Since the use of the SVM in spheroidal coordinates properly accounts for the geometry of the particles, the method is applicable to a large range of shapes ranging from elongated prolate needles via spheres to flat oblate disks. The relation between geometric symmetries of particles …

Neuro Fuzzy Reasoning For Pattern Classification And Object Recognition., Jayati Ghosh Dr.

Doctoral Theses

In real world, pattern classification and object recognition problems are faced with fuzzi- ness that is connected with diverse facets of cognitive activity of the human being. An origin of sources of fuzziness is related to labels expressed in feature space as well as to labels of classes taken into account in classification and /or recognition procedures. Though a lot of scientific efforts have already been dedicated to pattern recognition problems, especially to classification procedures, still pattern recognition is confronted with a continuous challenge coming from a human being who can perform lot of ex- tremely complex classification tasks by …

Fluid-Structure Interaction In Taylor-Couette Flow, Martin Horst Willi Kempf

Doctoral Dissertations

The linear stability of a viscous fluid between two concentric, rotating cylinders is considered. The inner cylinder is a rigid boundary and the outer cylinder has an elastic layer exposed to the fluid. The subject is motivated by flow between two adjoining rollers in a printing press. The governing equations of the fluid layer are the incompressible Navier-Stokes equations, and the governing equations of the elastic layer are Navier's equations. A narrow gap, neutral stability, and axisymmetric disturbances are assumed. The solution involves a novel technique for treating two layer stability problems, where an exact solution in the elastic layer …

Factorization For High-Energy Scattering, Ian Balitsky

Physics Faculty Publications

I demonstrate that the amplitude for the high-energy scattering can be factorized into a product of two independent functional integrals over “fast” and “slow” fields which interact by means of Wilson-line operators—gauge factors ordered along the straight lines.

Dead Cats: The Dark Secrets Of Causality And Quantum Mechanics, John Vrakas '00

Undergraduate Review

No abstract provided.

Pressure-Induced Changes In Structural And Mechanical Properties Of Gallium Arsenide And Nanophase Silicon Carbide Using Parallel Molecular Dynamics Simulations., Alok Chatterjee

LSU Historical Dissertations and Theses

Large-scale parallel molecular-dynamics (MD) simulations are performed to investigate properties and processes in nanophase silicon carbide (n-SiC) and gallium arsenide (GaAs) under pressure. These simulations involve 10 6 atoms interacting via realistic interatomic potentials. Structure and sintering of crystalline n-SiC are also investigated with neutron scattering experiments performed at the Intense Pulsed Neutron Source Division (IPNS), Argonne National Laboratory. Both MD simulations and neutron scattering experiments indicate the onset of sintering around 1500K. During sintering, the pores shrink in size while maintaining their morphology: Their fractal dimension remains ∼2.4 and their surface roughness exponent is ∼0.45. The pair distribution functions …

M1 Strength Distributions In Deformed Nuclei., Thomas Georg Beuschel

LSU Historical Dissertations and Theses

The Elliott SU(3) Model, extended via pseudo-spin for heavy nuclei, is used to study low-lying magnetic dipole excitations in deformed nuclei which axe known as "scissors" modes. Proton and neutron degrees of freedom are handled explicitly and a system Hamiltonian that preserves SU(3) symmetry and one that includes single particle energies as well as quadrupole-quadrupole and pairing two-body interactions are considered. Starting from a basic nuclear Hamiltonian that preserves SU(3) symmetry, a microscopic interpretation of the "scissors" mode of the Two Rotor Model is realized through a linear mapping between invariants of the rotor group and SU(3). The model allows …

The Selective Digital Integrator: A New Device For Modulated Polarization Spectroscopy., Aljosa Vrancic

LSU Historical Dissertations and Theses

A new device, a selective digital integrator (SDI), for the acquisition of modulated polarization spectroscopy (MPS) signals is described. Special attention is given to the accurate measurement of very small (AC component of interest $<$10$\sp{-3}$ x DC component), rapidly modulated ($\sim$50 kHz) signals at or below noise levels. Various data acquisition methods and problems associated with the collection of modulated signals are discussed. The SDI solves most of these problems and has the following advantages: it provides the average-time resolved profile of a modulated signal; it eliminates errors if the modulation is not sinusoidal; it enables separate measurements of the various phases of the signal modulation cycle; it permits simultaneous measurement of absorption, circular dichroism (CD) and linear dichroism (LD) spectra; it facilitates 3-D absorbance measurements; it has a wide gain-switching-free dynamic range (10 orders of magnitude or more); it offers a constant S/N ratio mode of operation; it eliminates the need for photomultiplier voltage feedback, and it has faster scanning speeds. The time-resolution, selectivity, wide dynamic range, and low-overhead on-the-fly data processing are useful for other modulated spectroscopy (MS) and non-MS experiments such as pulse height distribution and time-resolved pulse counting measurements. The advantages of the MPS-SDI method are tested on the first Rydberg electronic transitions of (+)-3-methylcyclopentanone. The experimental results validate the predicted SDI capabilities. However, they also point to two difficulties that had not been noted previously: the presence of LD in a gaseous sample and a pressure-dependence of the relative peak heights of the CD spectrum. Models for these anomalies are proposed. The presence of the oscillatory LD (but not an LD background) is explained with a sample cell model based on the observed polarization-dependent time-resolved profiles of transmitted light intensity. To obtain expressions for these intensities, a theoretical background, which provides a new approach to the treatment of light/matter interaction, is included as an Appendix. To explain the second anomaly, present only at high optical densities, a model based on the presence of scattered light is introduced and verified. The mode of correction for the scattering problem is outlined.

Nanostructure Modeling In Oxide Ceramics Using Large Scale Parallel Molecular Dynamics Simulations., Timothy J. Campbell

LSU Historical Dissertations and Theses

The purpose of this dissertation is to investigate the properties and processes in nanostructured oxide ceramics using molecular-dynamics (MD) simulations. These simulations are based on realistic interatomic potentials and require scalable and portable multiresolution algorithms implemented on parallel computers. The dynamics of oxidation of aluminum nanoclusters is studied with a MD scheme that can simultaneously treat metallic and oxide systems. Dynamic charge transfer between anions and cations which gives rise to a compute-intensive Coulomb interaction, is treated by the O(N) Fast Multipole Method. Structural and dynamical correlations and local stresses reveal significant charge transfer and stress variations which cause rapid …

The Grizzly, November 5, 1997, Paul Guidry, Michael Bauer, Melinda Albert, Arathi Reddy, Paul Bashus, Rob Bishop, Mark Bernheim, John Shoen, Lou Nemphos, Molly Jennings, Rebecca Class, Jay Wisnosky, Kim Inglot, Karen Hollinger, Jay Wilkes, Jacqueline Colvin, Jesse Federman, Kurt Miller, Kevin Mcgovern, Stephanie Palmer

Ursinus College Grizzly Newspaper, 1978 to Present

Distinguished Alumni Return for Symposium • Ursinus Students and Faculty Attend Million Woman March • More Grants Received by Ursinus • Student's Perseverance Rewarded • Test the Waters this Spring • Opinion: Faculty Responds to Curriculum Questions; Tired of Falling Asleep? • Stress Management • November Stress • Oedipus! Lives • There's Something Brewing in The Java Trench • What's with The Giant Green Gymnasium Anyway? • Ursinus: The Pseudo Liberal Arts College • Bears' Swimmers Kick Back at Dickinson Relay Carnival • Men's Soccer Continues to Struggle • Player Profiles: Jill Grau; Megan Larkin

Intrinsic Decoherence In Mesoscopic Systems, P. Mohanty, E. M.Q. Jariwala, Richard A. Webb

Faculty Publications

We present measurements of the phase coherence time τ_φ in six quasi-1D Au wires and clearly show that τ_φ is temperature independent at low temperatures. We suggest that zero-point fluctuations of the phase coherent electrons are responsible for the observed saturation of τ_φ. We introduce a new functional form for the temperature dependence and present the results of a calculation for the saturation value of τ_φ. This explains the observed temperature dependence of our samples as well as many 1D and 2D systems reported to date.

Snow And Ice Thickness Distributions In The South Polar Pacific Ocean, Ute Adolphs

Theses (Unassigned)

Two sets of snow and ice thickness data of antarctic sea ice are presented in this study: drilling profiles on individual sea ice floes and spatially more extensive shipboard observations are investigated in order to reveal spatial and temporal characteristics of sea ice. The data were acquired between 1993 and 1995 in the Ross and the Amundsen/Bellinghausen Seas, two different regions of the south polar Pacific Ocean. Sea ice characteristics as well as their spatial distribution and temporal evolution are derived from the data sets. Strong regional trends are observed in ice thickness distributions of the drilling data. A spatial …

An Investigation Of Cusp Latitude Magnetosphere-Ionosphere Physics: A Time Series Analysis Approach, Curt A. Szuberla

Theses (Unassigned)

The shocked solar wind plasma of the magnetosheath has direct access to the Earth's high-latitude ionosphere and upper atmosphere only through the magnetospheric cusps. The interaction of solar and terrestrial plasmas and fields in these regions has made them an obvious choice for the study of coupling processes in the geospace environment. Some of the information regarding these processes is manifest in the transmission and generation of wave energy, a portion of which can be detected by ground-based magnetometers. In the present day, records of the magnetic field are stored in a digital format; therefore, some form of signal processing …

Response Of Outer Radiation Belt Electrons To A Magnetic Storm, Donald Hugh Brautigam

Doctoral Dissertations

To advance our understanding of the magnetic storm dynamics of the outer radiation belt relativistic electrons, the magnetic storm which commenced on 9 October 1990 was analyzed in detail using data from the Combined Release and Radiation Effects Satellite (CRRES) and the Los Alamos National Laboratory geosynchronous satellite 1989enspace 046. Electron differential flux was transformed into phase space density as a function of the three adiabatic invariants. The invariants were determined by magnetic field data from CRRES and the Tsyganenko 1989 Kp driven model. The unique work of this thesis is the storm time radial diffusion modeling performed using time …

How Much Of The Nucleon Spin Is Carried By Glue?, Ian Balitsky, Xiangdong Ji

Physics Faculty Publications

We estimate in the QCD sum rule approach the amount of the nucleon spin carried by the gluon angular momentum: the sum of the gluon spin and orbital angular momenta. The result indicates that gluons contribute at least one half of the nucleon spin at the scale of 1GeV².