Digital Commons Network^™

Water Masers In W49n - The Youngest Stellar Jet?, Mordecai-Mark Mac Low, Moshe Elitzur

Physics and Astronomy Faculty Publications

Observations by Gwinn, Moran, and Reid of the proper motions of water masers in W49N show that they have an elongated distribution expanding from a common center. Features with high space velocity only occur far from the center, while low-velocity features occur at all distances. It is proposed that water masers in star-forming regions occur in expanding shells swept up by high-velocity winds from young, massive stars during the early phases of the expansion. In W49N, confinement of the bubble by a density distribution with an axial cavity can explain both the velocity field and the shape of the maser …

Prediction Of Paper Color: A Process Simulation Approach, Mayank Chaturvedi

Masters Theses

A simulation model was developed for a dye mixing process and for the prediction of the optical properties of the paper. The model was integrated with the MAPPS (Modular Analysis of Pulp and Paper Systems) simulation software package. The model was validated using dyed handsheets made in a laboratory and dyed paper made on a pilot papermachine. Validation comprised of prediction of the optical properties of the handsheets and the machine-made paper which contained various combinations of three non-fluorescent dyes. Sheet reflectances were predicted at 20 nanometer intervals for discrete light wavelength range of 400 to 700 nanometers and verified …

Limaçon Of Pascal Locus Of The Complex Refractive Indices Of Interfaces With Maximally Flat Reflectance-Versus-Angle Curves For Incident Unpolarized Light, R. M.A. Azzam

Electrical Engineering Faculty Publications

For an interface between two isotropic media the power reflectance R_v (ø) is an even function, R_v (ø) = R_v (--), of the angle of incidence ø; hence all the odd derivatives, R_v⁽ⁿ⁾ = dⁿ R_v /døⁿ (n odd), are identically 0 at ø = 0, independent of the incident polarization v. When the incident light is unpolarized (v = u), the second derivative, R_u⁽²⁾, is also 0 at ø = 0, so that the flatness of the R_u -versus-ø curve …

Crystalline Orientations Of Tl2Ba2Ca2Cu3OΧ Grains On Mgo, Srtio3, And Laalo3 Substrates, Sy_Hwang Liou, C.Y. Wu

Sy-Hwang Liou Publications

Crystalline orientations of Tl₂Ba₂Ca₂Cu₃O_χ grains in magnetron sputtered films on MgO (001), SrTiO₃ (001), and LaAlO₃ (001) substrates were investigated by scanning electron microscopy. In contrast to the nearly single crystalline films on the lattice matched substrates SrTiO₃ and LaAlO₃, films on the MgO (001) substrate, being polycrystalline in nature, exhibit several preferred in-plane grain orientations. These orientations agree well with a simplified theory of near-coincidence site lattices between Tl₂Ba₂Ca₂Cu₃O_χ and MgO.

Some Stability Problems In Droplet Formation And Breakup (Report Lstm 351/T/92)., Nihad E. Daidzic

Aviation Department Publications

In this study the instability of droplets and cylindrical jets is investigated. The understanding of these processes has both academic and practical value. Instability of cylindrical jets is theoretically investigated for infinitesimal and finite, but small initial amplitudes (linear and nonlinear stability). For droplets, only linear theory is presented. It is assumed that the capillary force play a dominant role. It is determined that the viscosity exerts a damping effect. In the first section we give an introduction, after which the linear stability theory of cylindrical liquid jets is presented. In the third section the nonlinear jet stability theory is …

Tamm States In Finite Semiconductor Superlattices: Influence Of Accumulation And Depletion Layers, Roger H. Yu

All Faculty Scholarship for the College of the Sciences

We discuss the electronic-level structure of finite semiconductor superlattices and the influence of accumulation and depletion regions on the surface localized states (Tamm states). Exact solutions of the Poisson and Schrödinger equations are obtained self-consistently, through use of a nonuniform jellium model. Both high-energy and low-energy Tamm states are found.

Rayleigh-Brillouin Scattering To Determine One-Dimensional Temperature And Number Density Profiles Of A Gas Flow Field, James A. Lock, Richard G. Seasholtz, W. Trevor John

Physics Faculty Publications

Rayleigh-Brillouin spectra for heated nitrogen gas were measured by imaging the output of a Fabry-Perot interferometer onto a CCD array The spectra were compared with the theoretical 6-moment model of Rayleigh-Brillouin scattering convolved with the Fabry-Perot instrument function. Estimates of the temperature and a dimensionless parameter proportional to the number density of the gas as functions of position in the laser beam were calculated by least-squares deviation fits between theory and experiment.

Thermal Rounding Of The Charge Density Wave Depinning Transition, Alan Middleton

Physics - All Scholarship

The rounding of the charge density wave depinning transition by thermal noise is examined. Hops by localized modes over small barriers trigger ``avalanches'', resulting in a creep velocity much larger than that expected from comparing thermal energies with typical barriers. For a field equal to the $T=0$ depinning field, the creep velocity is predicted to have a {\em power-law} dependence on the temperature $T$; numerical computations confirm this result. The predicted order of magnitude of the thermal rounding of the depinning transition is consistent with rounding seen in experiment.

Selective Area, Synchrotron Radiation Induced, Delta Doping Of Silicon, R.A. Rosenberg, S.P. Frigo, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

We have used broadband synchrotron radiation to induce selective area surface doping of boron into silicon. The source of the boron was nido-decaborane (B₁₀H₁₄) adsorbed on Si(111) at 100 K. Irradiation caused decomposition of the adsorbed molecule which lead to an enhanced concentration of free boron in the irradiated area. Using Si 2p core level photoelectron spectroscopy, the surface chemical composition and Fermi level position in both the irradiated and unirradiated regions were determined. The downward movement of the Fermi level was greater in the irradiated region than in the unirradiated region, and greater …

Evidence For The Formation Of Metallic Mercury Overlayers On Si(111), Dongqi Li, Jiandi Zhang, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

A strongly chemisorbed Hg species is observed following the adsorption of Hg on Si(111) at 110 K. This strongly chemisorbed Hg species and subsequently weakly chemisorbed Hg species are observed to be metallic in the photoemission final state as determined by resonant photoemission and the reduction of photovoltaic charging. We postulate that the strongly chemisorbed Hg species on Si(111) is more metallic at dilute coverages than Hg adsorbed on Cu(100).

Mutual Information, Strange Attractors, And The Optimal Estimation Of Dimension, J. M. Martinerie, Alfonso M. Albano, A. I. Mees, P. E. Rapp

Physics Faculty Research and Scholarship

It has been shown that the appropriate setting of data windows is crucial to a successful estimation of a time-series correlation dimension using the Grassberger-Procaccia algorithm [Physica 9D, 189 (1983); Phys. Rev. Lett. 50, 346 (1983)], and it has been proposed that the first minimum of the corresponding mutual-information function may be an appropriate window value. We have tested this hypothesis against data generated by the Rossler equations, the Lorenz equations, and a three-dimensional irrational torus. We conclude that mutual information is not consistently successful in identifying the optimal window.

Incorporation Of Si And Al In Low Temperature Mbe Gaas, M. O. Manasreh, K. R. Evans, C. E. Stutz, David C. Look

Physics Faculty Publications

The localized vibrational modes (LVMs) of silicon donor (Si_Ga) and aluminum isovalent (Al_Ga) impurities in molecular beam epitaxial GaAs layers grown at various temperatures are studied using the infrared absorption technique. It is found that the total integrated absorption of these impurities LVMs is decreased as the growth temperature decreases. This finding suggests a nonsubstitutional incorporation of Si and Al in GaAs layers grown at 200 °C. On the other hand, a subtitutional incorporation is obtained in GaAs layers grown at temperatures higher than 350 °C. A recovery of the Si_Ga LVMs in GaAs layers …

Senior Theses: Department Of Physical Sciences, Patrick M. Higgins, Timothy Howard, Leah Carol Ross

Morehead State Theses and Dissertations

1992 Senior Theses from the Department of Physical Science at Morehead State University.

The Abundance, Diversity, and Stratigraphy of the Upper Crab Orchard Formation, Lewis County, Kentucky by Patrick M. Higgins.

The Modification of Flemion for Use in a Solid Electrolyte Battery by Timothy Howard.

Simple Analog Computers by Leah Carol Ross.

Dephasing Processes In Glasses With Strong Strain Interactions, Ulrich Zürcher, R. Silbey

Physics Faculty Publications

Spectral diffusion decay is calculated for a glass modeled by two level systems which are strongly coupled to phonons. The spin-phonon interaction induces an effective spin-spin interaction which dominates the energy scale. We show that spectral diffusion is a property of macroscopic local fields which fluctuate on time scales that are much longer than the spin-phonon relaxation time T1. We assume for the spectral diffusion a Gaussian distribution and derive a self-consistent equation for its variance which is nonlocal in time. At high temperatures, the variance grows linearly with time while at low temperatures, we find strong deviations from simple …

Assessing The Contributions Of Surface Waves And Complex Rays To Far-Field Mie Scattering By Use Of The Debye Series, Edward A. Hovenac, James A. Lock

Physics Faculty Publications

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye-series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with those of the Debye series. Interference effects among surface waves, complex rays, and geometrical rays are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface-wave-geometrical-ray-interference pattern are presented.

Optical Caustics In Natural Phenomena, James A. Lock, James H. Andrews

Physics Faculty Publications

When observing a distant point source of light through a water droplet adhering to a pane of glass near one's eye or the scattering of light from raindrops, one often sees optical caustics. In this paper, diffraction integrals are used to investigate these caustics. The caustic shapes are related to divergences in the stationary phase method for approximating the diffraction integrals. These divergences correspond to the coalescing of two or more geometrical light rays in ray optics or the coalescing of two or more regions of stationary phase in wave optics. The number of coalescing light rays is related to …

Thermal Conductivity Of Thermoelectric Si0.8‐Ge0.2 Alloys, D. P. White, P. G. Clemens

Physics Faculty Publications

The thermal conductivity of heavily doped, n-type Si-Ge alloys has been studied from 300 to 1200 K. The scattering rate of several phonon scattering mechanisms has been calculated, including intrinsic scattering, mass defect and distortion scattering, phonon-electron scattering, and scattering by inclusions. These rates were then used to calculate the lattice thermal conductivity. The electronic component of the thermal conductivity was calculated from the calculated Lorenz ratio and measured values of the electrical conductivity. The total thermal conductivity was then compared to measured values for a specimen studied by Vining et al.

Incorporation Of Silicon And Aluminum In Low-Temperature Molecular-Beam Epitaxial Gaas, M. O. Manasreh, K. R. Evans, C. E. Stutz, David C. Look, Joseph Hemsky

Physics Faculty Publications

The localized vibrational modes (LVMs) of silicon donor (Si_Ga) and aluminum isovalent (Al_Ga) impurities in molecular beam epitaxial GaAs layers grown at various temperatures are studied using the infrared absorption technique. It is found that the total integrated absorption of these impurities LVMs is decreased as the growth temperature decreases. This finding suggests a nonsubstitutional incorporation of Si and Al in GaAs layers grown at 200 °C. On the other hand, a subtitutional incorporation is obtained in GaAs layers grown at temperatures higher than 350 °C. A recovery of the Si_Ga LVMs in GaAs layers …

Review: 'Optical Fiber Communications' (2nd Edition), By Gerd Keiser, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

If first impressions are worth anything (and they usually are), I would have to admit that my first impression of the second edition of Gerd Keiser's now popular text Optical Fiber Communications was quite good. My compliments are hereby extended to the publisher for choosing a rather handsome cover and dust jacket. It stands in strong contrast to the text's first edition, which still ranks as probably the ugliest book I own, with color choices ranging from dull cream and "baby" blue to pale pink! I am now happy to say that this older version has been discretely·retired to the …

The Three-Line Magnetic Hyperfine Spectrum Of 57Fe, Norman A. Blum, Richard B. Frankel

Physics

Longitudinal magnetization of a ⁵⁷Co in iron metal foil source and an iron metal foil absorber in a uniform external magnetic field results in a simple three-line magnetic hyperfine absorption spectrum. Measurement of the spectral splitting as a function of applied magnetic field yields the ⁵⁷Fe excited-and ground-state g-factors.

An Embedded Ring Approach To The Vibrational Dynamics Of Disordered Two-Dimensional Materials, Timothy Edwin Doyle

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A theoretical approach was developed to model the vibrational dynamics of amorphous, two-dimensional materials. The materials were modeled as continuous random networks (CRN's) comprising an assemblage of planar rings of diverse size. In-plane vibrational modes for symmetric 4-, 5-, 6-, 7-, and 8-membered rings were examined. Vibrational states of isolated rings were modified by coupling the rings to a continuous network to represent rings embedded in a CRN. An effective force constant was used to couple the ring vibrations to the network's collective motions. Potentials were approximated with the use of a central force model (bond-stretching force constant) and a …

Multiplet Fine Structure Of The Gd And Tb 5p Levels, Dongqi Li, Peter A. Dowben, M. Onellion

Peter Dowben Publications

Fine structure is observed in the photoemission of Gd and Tb 5p levels as a result of multiplet splitting. These splittings are the consequence of different J final states that occur as a result of interactions with partly filled 4f and/or 5d levels.

Demonstrating The Utility Of Boron Based Precursor Molecules For Selective Area Deposition In A Scanning Tunneling Microscope, F. Keith Perkins, M. Onellion, Sunwoo Lee, Peter A. Dowben

Peter Dowben Publications

The scanning tunneling microscope (STM) can be used to selectively deposit material from a gaseous precursor compound. Ultra-small (less than a 100 nm across) spatial dimensions for selective area deposition may be achieved by this means. In this paper we outline a scheme for selecting and designing main group cluster compounds and organometallics for this type of selective area deposition using nido-decaborane(l4) as an example.

Transmission Studies Of Explosive Vaporization Of A Transparent Liquid Film On An Opaque Solid Surface Induced By Excimer-Laser-Pulsed Irradiation, P.T. Leung, Nhan Do, Leander Klees, Wing P. Leung, Frank Tong

Physics Faculty Publications and Presentations

Examines the dynamics of the explosion of a liquid film by an ultraviolet excimer pulsed laser studied experimentally on top of an amorphous silicon film deposited on fused quartz. Background on thermal physics of superheated pure or mixed liquids; Techniques for surface temperature measurement; Experimental of probe laser and pulsed excimer laser.

Automated Seebeck Measurements Applied To Conducting Ceramics, J. S. Shapiro

Opportunities for Undergraduate Research Experience Program (OURE)

The Seebeck coefficient (also known as thermopower) is important in the characterization of conducting ceramics because it is very sensitive to the electronic structure. An apparatus was built during the Fall of 1990 and Spring of 1991 which was designed to measure the Seebeck coefficient in small high-resistivity samples in the temperature range from 80 K to 450 K. A reproducible thermocouple-to-sample electrical and thermal contact technique was found to be important to data accuracy but difficult to achieve. The goals of this project were to improve the thermocouple block design to give better thermal and electrical contact with the …

Design And Development Of A Superconducting Induction Motor, Terry Bowness

Opportunities for Undergraduate Research Experience Program (OURE)

The discovery of high-T_c superconductors has led to the development of a number of experimental superconducting motors. This report documents the design, construction, and methods of evaluating the performance of an induction motor with a high-T_c superconducting rotor. While others have utilized the Meissner effect, our superconducting motor works due to Lenz’s law. In theory such a device will act as an induction motor only during start-up, after which its behavior is more like that of a synchronous machine. With a one-pole copper squirrel cage providing start-up torque two high-T_c discs encased in the rotor core act …

Bulk And Surface Singularity Indices In The Alkali Metals, G. K. Wertheim, D. Mark Riffe, P. H. Citrin

All Physics Faculty Publications

Photoemission data from (110) films of Li, Na, and Rb, in which the signal from the first atomic layer is well resolved, show that the core-hole-screening singularity index is ∼40% larger at the surface than in the bulk for all three metals. This result, which is indicative of the more atomiclike character of metal surface atoms, in general, is particularly large for the alkali metals because their conduction-electron screening is mainly s-like. In addition to quantifying the difference in screening at the surface, the data provide bulk singularity indices of 0.22, 0.16, and 0.14 for Li, Na, and Rb, respectively. …

Anomalous Dipolar Flexoelectric Effect In A Nematic Main-Chain Polymer, Rolfe G. Petschek, Eugene M. Terentjev

Faculty Scholarship

An anomalously large flexoelectric effect is predicted in the nematic phase of thermotropic main-chain polymers, which have a defined orientation of subsequent monomers bonded on the chain. We identify two different ranges of order parameters. When the persistence length of the chain in the direction parallel to the order parameters is larger than a monomer length but not too long (small order parameter), the longitudinal flexoelectric coefficient f is proportional to this exponentially large persistence length, assuming that the polymers are many persistence lengths long. This result corresponds to the simple estimation that relates flexoelectric coefficients to the Frank elastic …

Electron Production In Proton Collisions With Atoms And Molecules: Energy Distributions, M. Eugene Rudd, Y.-K. Kim, D. H. Madison, Timothy J. Gay

Timothy J. Gay Publications

All known data on the energy distribution of secondary electrons from collisions of protons with atoms and molecules have been reviewed and differential cross sections have been collected. The two experimental methods used to obtain the data are discussed and possible sources of error pointed out. Theoretical treatments are reviewed and several methods of checking the consistency of the data are discussed. Two semiempirical models have been chosen to represent the differential cross sections, and parameters for these models are given which fit the average of the experimental data, subject to known constraints. Recommended values of differential cross sections are …

Scaling Dynamics Of Aerosol Coagulation, B. J. Olivier, C. M. Sorensen, Thomas W. Taylor

Physics Faculty Publications

A combination of static and quasielastic light scattering and the theory of scaling solutions to Smoluchowski's equation was used to determine the absolute coagulation rate K'0 and kernel homogeneity lambda of a coagulating liquid-drop aerosol. Droplet sizes ranged from 0.23 to 0.42-mu-m, implying Knudsen numbers in the range 0.26 and 0.14. The temporal evolution of the number concentration M0 and the modal radius r(M) of an assumed zeroth-order log-normal distribution showed near-power-law behavior similar to that predicted by the scaling theory. From the temporal scaling behavior of M0(t) and r(M)(t), the absolute coagulation rate was calculated. The coagulation rates from …