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Performance Analysis Of The Speckle Holography Image Reconstruction Technique, Rudolf N. Vonniederhausern Dec 1991

Performance Analysis Of The Speckle Holography Image Reconstruction Technique, Rudolf N. Vonniederhausern

Theses and Dissertations

In speckle holography, short exposures frames along with wave front measurements allow post processing image reconstruction. With speckle holography the amplitude of high spatial frequencies is boosted to allow resolution out to the diffraction limit of the telescope. To provide system parameters for the wave front sensor design, a software analysis program has been developed that provides the system transfer function as a function of the number and size of sensor subapertures and sensor noise. Trends in the ratio of the atmospheric coherence diameter to wave front subaperture size and the effect on the system transfer function have been obtained. …


Optical Image Segmentation Using Wavelet Correlation, Steven D. Pinski Dec 1991

Optical Image Segmentation Using Wavelet Correlation, Steven D. Pinski

Theses and Dissertations

This research introduces an optical method of segmenting potential targets using wavelet analysis. Implementation of an optical Harr wavelet is fulfilled using a magneto-optic spatial light modulator (MOSLM). Two methods of controlling wavelet dilation are explored: (1) spatial filtering of a ternary modulated MOSLM; (2) a single aperture positioned in front of a binary modulated MOSLM. Segmentation is performed through Vander Lugt correlation of a binarized image with a binarized optical wavelet. Three different image binarization methods are investigated for use in the correlation scheme: (1) average pixel value over an entire scene; (2) localized 4 x 4 pixel average …


Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi Dec 1991

Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi

Theses and Dissertations

Low temperature photoluminescence studies were performed on nine silicon germanium alloy superlattice samples. The luminescence spectra showed sharp peaks in the 0.95 to 1.05 eV energy range, and a broad band located 0.05 to 0.12 eV below the alloy bandgap. The sharp peaks were identified as transitions associated with impurity bound excitons. The linewidth was about 10 times that in pure silicon; in addition, the peaks shifted to lower energy as the sample temperature was raised from 1.4 to 15 K. These features were attributed to effects of random distribution of atoms in the alloy. The broad band shifted to …


An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii Dec 1991

An Analysis Of One-Dimensional Models Of The Insulating And Conducting Priz, Joseph W. Cook Iii

Theses and Dissertations

This study attempted to analytically reproduce experimental and analytical data, on the single-insulated and conducting PRIZ, presented in 1987 and 1988 by the Soviet scientists Bliznetsov et al. Our onedimensional analytical models, derived from earlier Soviet reports, have consistently reproduced previously reported data on the PRIZ. In this study, the same codes were successfully used to analyze the effects of injection at high and low intensity exposures (30 µW/cm2 to 500 mW/cm2) Although the codes qualitatively duplicated the nature of the space charge distribution in the single-insulated and conducting PRIZ, our quantitative results were significantly different from …


Self-Pumped Phase-Conjugate Twyman-Green Interferometry Using A Batio3 Crystal, Deborah A. Determan Dec 1991

Self-Pumped Phase-Conjugate Twyman-Green Interferometry Using A Batio3 Crystal, Deborah A. Determan

Theses and Dissertations

The Air Force uses optical imaging systems in many fields such as communications, target recognition, and missile guidance. For proper execution of these applications, the optical imaging systems use in these fields must be of extremely high quality so that an ideal image is obtained. In divergent beam configurations, this type of interferometer would eliminate the need for high quality reference optics needed in conventional Twyman-Green interferometry. The objective of this thesis is to demonstrate phase conjugate Twyman-Green interferometry using a barium titanate (BaTiO3) crystal as the phase conjugating mirror in the reference arm of the interferometer and …


Photoluminescence Spectroscopy Of Mbe Grown Gallium Antimonide, John A. Dorian Dec 1991

Photoluminescence Spectroscopy Of Mbe Grown Gallium Antimonide, John A. Dorian

Theses and Dissertations

Experimental data are presented for the energy levels of the native acceptor and bound exciton emissions of GaSb grown by MBE and studied with low temperature photoluminescence (PL) spectroscopy. The undoped GaSb emissions showed a donor-acceptor pair transition with an observed emission peak at 776 meV, a peak at 716 meV usually associated with the ionization level of the acceptor, and bound exciton transitions in the energy range from 796 to 804 meV. Other unidentified peaks were observed at about 805 meV. Temperature and power dependence studies of the acceptor peak confirmed donor-acceptor pair (DAP) behavior. A GaSb sample grown …


Vibrational Energy Transfer In Bromine Monofluoride, Tim L. Thompson Dec 1991

Vibrational Energy Transfer In Bromine Monofluoride, Tim L. Thompson

Theses and Dissertations

Bromine monofluoride (BrF), an interhalogen molecule, is a prospective chemical laser candidate. This study continues research begun in characterizing radiative and collisional dynamics in BrF. Vibrational energy transfer of BrF is studied using time resolved laser induced fluorescence (LIF) techniques and observing the spectrally resolved emission. First, vibrational transfer induced by the BrF production mix is determined to follow the Montroll- Shuler model and Landau-Teller scaling with a fundamental rate coefficient of kv(1,0) = (4.0) x 10-12 cm3/(molecules seconds). Also, rate coefficients for the rare gases were found to scale with the reduced mass of the collision …


Magnetic And Structural Properties Of Co/Cr Multilayers With In-Plane Anisotropy, D. Wang, David J. Sellmyer Nov 1991

Magnetic And Structural Properties Of Co/Cr Multilayers With In-Plane Anisotropy, D. Wang, David J. Sellmyer

David Sellmyer Publications

Previously we studied the effect of Cr spacer layer on in-plane coercivity in Co/Cr multilayered films. It was found that the high coercivity is related to the easy axis in-plane orientation and the character of the composition modulation. In this paper, the dependence of the saturation magnetization as a function of Co layer thickness is used to study the interface structure. The layer structure is confirmed by small angle x-ray diffractometry for typical films. The magnetic interaction among the grains is studied by examining deviation from the behavior predicted by the Wohlfarth model for noninteracting single-domain particles. Journal of Applied …


Development Of The Gd(0001) Band Structure With Film Thickness, Dongqi Li, W. Hutchings, Peter A. Dowben, Rong-Tzong Wu, C. Hwang, M. Onellion, A.B. Andrews, J.L. Erskine Nov 1991

Development Of The Gd(0001) Band Structure With Film Thickness, Dongqi Li, W. Hutchings, Peter A. Dowben, Rong-Tzong Wu, C. Hwang, M. Onellion, A.B. Andrews, J.L. Erskine

Peter Dowben Publications

By growing gadolinium films on W(110), it has been possible to observe the development of the Gd(0001) band structure with increasing film thickness. The changes in the 5d bands as a result of exposure to oxygen or the development of the valence-band structure with increasing film thickness lead to changes in the 5p multiplet oscillator strengths. These changes are a result of the influence of the band structure upon the final-state effects that give rise to such multiplet structures. This study provides conclusive evidence that there is a 5d contribution to the shallow 5p multiplet photoemission …


Fabricating Magnetic Co-Ni-C Thin-Film Alloys By Organometallic Chemical Vapor Deposition, Yoon-Gi Kim, Dongjin Byun, C. Hutchings, Peter A. Dowben, H. Hejase, K. Schröder Nov 1991

Fabricating Magnetic Co-Ni-C Thin-Film Alloys By Organometallic Chemical Vapor Deposition, Yoon-Gi Kim, Dongjin Byun, C. Hutchings, Peter A. Dowben, H. Hejase, K. Schröder

Peter Dowben Publications

We have deposited CoxNiy-C films with a variety of compositions to verify dependence of the saturation magnetization on the composition. These experiments suggest that we can produce CoxNiy-C films with a variety of magnetic properties. The CoxNiy-C films were fabricated by ultraviolet decomposition of cobaltocene and nickelocene. We demonstrated that the photolytic decomposition of these metallocenes produces cyclopentadienyl (C5H5) species, consistent with recent studies of the energetics of the ligand metal bonds.


The Process-Controlled Magnetic Properties Of Nanostructured Co/Ag Composite Films, Sy_Hwang Liou, S. Malhotra, Z.S. Shan, David J. Sellmyer, S. Nafis, John A. Woollam, C.P. Reed, R.J. Deangelis, G.M. Chow Nov 1991

The Process-Controlled Magnetic Properties Of Nanostructured Co/Ag Composite Films, Sy_Hwang Liou, S. Malhotra, Z.S. Shan, David J. Sellmyer, S. Nafis, John A. Woollam, C.P. Reed, R.J. Deangelis, G.M. Chow

Sy-Hwang Liou Publications

Nanostructured Co/Ag composite films were prepared by magnetron sputtering using a single target. The average crystallite sizes of Co and Ag in the films depend on the deposition conditions. As the substrate temperature increases from 100 °C to 600 °C, the average Ag crystallite size increases from 39 to 452 Å, and the average Co crystallite size increases from Å in the film with 39 vol. % of Co. The films with 39 vol. % of Co and prepared at 400 °C substrate temperature showed a maximum magnetic coercivity of 565 Oe at 6 K. We have studied the correlation …


Temperature And Thickness Dependence Of Coercivity And Magnetization Of Co/Cu And Co/Si Multilayers, S. Nafis, John A. Woollam, Z.S. Shan, David J. Sellmyer Nov 1991

Temperature And Thickness Dependence Of Coercivity And Magnetization Of Co/Cu And Co/Si Multilayers, S. Nafis, John A. Woollam, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

Co/Cu and Co/Si multilayers of total thickness ~3000 Å were prepared by rf and dc magnetron sputtering. The nominal thicknesses of the individual layers were in the range of 4 to 100 Å. A large coercivity (Hc) at 10 K was observed for very thin layers of Co in Co/Cu samples, and it decreased with increase of the Co layer thickness. For very thin layers of Co in Co/Cu samples, the layer behaved superparamagnetically. Similar behavior was not to be observed in Co/Si samples. With increased substrate temperature (Ts) during deposition, Hc was …


Sputtering Pressure Effect On Microstructure Of Surface And Interface, And On Coercivity Of Co/Pt Multilayers, Ping He, William A. Mcgahan, S. Nafis, John A. Woollam, Z.S. Shan, Sy_Hwang Liou, F. Sequeda, T. Mcdaniel, H. Do Nov 1991

Sputtering Pressure Effect On Microstructure Of Surface And Interface, And On Coercivity Of Co/Pt Multilayers, Ping He, William A. Mcgahan, S. Nafis, John A. Woollam, Z.S. Shan, Sy_Hwang Liou, F. Sequeda, T. Mcdaniel, H. Do

Sy-Hwang Liou Publications

Thin Co/Pt multilayers were prepared on Si and glass substrates by sputtering with Ar pressures ranging from 2.5 to 15 mTorr. The bilayer structure of the samples was Co(3 Å)/Pt(15 Å)×17, and all samples had the easy axis of magnetization perpendicular to the sample surface as determined with a SQUID magnetometer. All samples retained the layered structure, as revealed by low-angle x-ray diffraction. In addition, diffraction peaks due to the formation of Co-Pt compounds (presumably at the interfaces between Co and Pt) were identified. The coercivity of samples changed from about 400 Oe for films deposited at low Ar sputtering …


Studies Of Domain Dynamics In Amorphous Dy/Fe Multilayers, Roger D. Kirby, J.X. Shen, Z.S. Shan, David J. Sellmyer Nov 1991

Studies Of Domain Dynamics In Amorphous Dy/Fe Multilayers, Roger D. Kirby, J.X. Shen, Z.S. Shan, David J. Sellmyer

Roger Kirby Publications

Compositionally-modulated Dy/Fe films were prepared by dc magnetron sputtering onto glass substrates. For this series of samples, the Dy thickness was fixed at 5 Å, while the Fe thickness was varied from 4 to 6 Å. To study the magnetization reversal, the samples were first saturated. The magnetic field was then reversed to a value near the coercive field, and the Kerr rotation was measured as a function of time after reversal. We interpret our results in terms of the model of domain reversal first described by Fatuzzo for ferroelectrics. For some Fe thicknesses, we found that the reversal process …


Temperature And Layer-Thickness Dependencies Of Kerr Rotation In Dy/Co Multilayers, Z.S. Shan, J.X. Shen, Roger D. Kirby, Sy_Hwang Liou, David J. Sellmyer Nov 1991

Temperature And Layer-Thickness Dependencies Of Kerr Rotation In Dy/Co Multilayers, Z.S. Shan, J.X. Shen, Roger D. Kirby, Sy_Hwang Liou, David J. Sellmyer

Sy-Hwang Liou Publications

Amorphous Dy/Co multilayers with the individual layer thickness between 4 and 10 Å in steps of 0.5 to 1 Å were studied systematically over the temperature range 100–300 K. The Kerr rotation increases as temperature decreases, or as Co content increases and the coercivity increases both in the low temperature region and in the vicinity of the compensation point. These characteristics were analyzed in terms of simple models of the magnetic structure and magnetization reversal.


Single-Electron Charging Effects In Insulating Wires, Venkat Chandrasekhar, Zvi Ovadyahu, Richard A. Webb Nov 1991

Single-Electron Charging Effects In Insulating Wires, Venkat Chandrasekhar, Zvi Ovadyahu, Richard A. Webb

Faculty Publications

We present measurements of the transport properties of 0.75-μm-long, narrow, insulating indium oxide wires and rings. These devices have no apparent tunnel barriers, yet they exhibit effects similar to those found in series arrays of very small-capacitance tunnel junctions: highly nonlinear I-V characteristics and a zero-bias conductance which is periodic in a voltage applied by means of a lateral gate. These effects are due to the influence of single-electron charging on transport through localized states in the insulating regime.


Dmsp F7 Observations Of A Substorm Field‐Aligned Current, R. E. Lopez, Harlan E. Spence, C. Meng Nov 1991

Dmsp F7 Observations Of A Substorm Field‐Aligned Current, R. E. Lopez, Harlan E. Spence, C. Meng

Physics & Astronomy

In this paper we present observations of a substorm field-aligned current (FAC) system that DMSP F7 traversed just after 0300 UT on April 25, 1985. Ground magnetometer data show that a major substorm was in progress at that time and that DMSP F7 flew through a region of predominantly upward FAC. The DMSP F7 magnetic field data are consistent with this interpretation. The precipitating particle data suggest that there were three distinct large-scale FAC systems. In ascending latitude these were a downward current, an upward current, and a paired upward/downward current system. We identify the first current, which was coincident …


Pyro-Electro-Optic Phase Gratings, Stephen Ducharme Nov 1991

Pyro-Electro-Optic Phase Gratings, Stephen Ducharme

Stephen Ducharme Publications

A new physical mechanism is proposed for generating transient phase gratings in transparent pyroelectric materials. The mechanism combines the pyroelectric and electro-optic effects to convert spatial intensity variations into transient phase gratings. The grating diffraction efficiency increases with a figure of merit that is proportional to the pyroelectric, electro-optic, and absorption coefficients and is inversely proportional to the specific heat. The grating response time is proportional to the specific heat and inversely proportional to the thermal conductivity. Diffraction efficiencies that approach unity are predicted in several readily available electro-optic materials with modest pulse energies from Q-switched Nd:YAG lasers. Observation …


Variation Of Superparamagnetic Properties With Iron Loading In Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt Nov 1991

Variation Of Superparamagnetic Properties With Iron Loading In Mammalian Ferritin, Richard B. Frankel, G. C. Papaefthymiou, G. D. Watt

Physics

The average blocking temperatures of ferritin molecules containing differing amounts of iron were determined by Mossbauer spectroscopy. The results imply that the magnetic anisotropy of the ferritin core particles is a function of particle volume. By addition of 57Fe to ferritin core particles it was determined that, at a given temperature within the superpara-magnetic temperature region, the “last-in” ferric ions have average relaxation times that are shorter than those of the bulk ferric ions.


The Behlen Observatory Variable Star Survey: First Results, Edward G. Schmidt Nov 1991

The Behlen Observatory Variable Star Survey: First Results, Edward G. Schmidt

Edward Schmidt Publications

Various light curve parameters are presented for the first 93 objects in a photometric survey of poorly studied variable stars. Stars from the General Catalogue of Variable Stars (GCVS) fainter than tenth magnitude, north of the equator which were classified as pulsating variables (but excluding the long period, semiregular, and irregular variables) were included. It is shown that two parameters, the acuteness and the rise time, are useful for characterizing the light curves. Several criteria are applied to the photometric data to test the classification of the stars. For 26 stars new or improved classifications are suggested. In particular, there …


Anyonic Superconductivity In A Modified Large-U Hubbard Model, Asim Gangopadhyaya, Prasanta K. Panigrahi Nov 1991

Anyonic Superconductivity In A Modified Large-U Hubbard Model, Asim Gangopadhyaya, Prasanta K. Panigrahi

Physics: Faculty Publications and Other Works

A modified large-U Hubbard model at half filling is analyzed by a mean-field approach. Preserving a local U(1) symmetry of the action, the fluctuations about half filling are studied in the spirit of the commensurate-flux-phase condition. The fluctuations then contribute a Chern-Simons term to the tree-level Lagrangian with a coefficient appropriate to that of a half fermion. With the Coulomb repulsion term, we study the low-energy excitations of the model and show the existence of superconductivity in the presence of a four-Fermi interaction term.


The Effect Of A Tilted Magnetic Field On The Equilibrium Of A Pure Electron Plasma, Grant W. Hart Nov 1991

The Effect Of A Tilted Magnetic Field On The Equilibrium Of A Pure Electron Plasma, Grant W. Hart

Faculty Publications

If the magnetic field in a pure electron plasma containment device is not aligned with the axis of the conducting walls, the electrons in the device will accumulate at the ends of the plasma where the magnetic field lines come closest to the walls and the electrons bound to the field lines can be closest to their image charges. If the plasma is also offset radially from the center (as with an l=1 diocotron mode), then more density will accumulate at one end than the other. As the plasma revolves around the center, the electrons will slosh from one end …


Change Of Magnetic Properties Of Th₂Fe₁₇ Due To Interstitial Solution Of C And N, T. H. Jacobs, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. Buschow Nov 1991

Change Of Magnetic Properties Of Th₂Fe₁₇ Due To Interstitial Solution Of C And N, T. H. Jacobs, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. Buschow

Chemistry Faculty Research & Creative Works

The changes in magnetic and crystallographic properties in the series Th2Fe17Cx and Th2Fe 17Nx have been studied. The changes in the latter series were also studied by 57Fe Mössbauer spectroscopy. The ultimate enhancements of the saturation moments in these series are 13% and 24%, respectively. This is much larger than observed previously in the corresponding rare-earth compounds, although the Curie temperature enhancements are of comparable magnitude. In the Th-Fe-C system a novel compound of the BaCd 11 type was found, having a Curie temperature around 370 K.


Solid State Proton Spin Relaxation And T-Butyl And Methyl Group Reorientation In 1-Bromo-2,4,6-Tri-T-Butylbenzene, Anne M. Fry, Peter A. Beckmann, Albert J. Fry, Peter C. Fox, Ari Isenstadt Oct 1991

Solid State Proton Spin Relaxation And T-Butyl And Methyl Group Reorientation In 1-Bromo-2,4,6-Tri-T-Butylbenzene, Anne M. Fry, Peter A. Beckmann, Albert J. Fry, Peter C. Fox, Ari Isenstadt

Physics Faculty Research and Scholarship

We have used the solid state proton spin relaxation technique to investigate the barriers for methyl and t-butyl group reorientation in polycrystalline 1-bromo-2,4,6-tri-t-butylbenzene. The barriers in the range of 15-19 kJ/mol (3-5 kcal/mol) are compared with those found in related molecules. It is shown that the neighboring ring bromine atom has an effect on the barrier for t-butyl group reorientation similar to that of a neighboring hydrogen atom despite the significantly larger van der Waals' radius of a bromine atom. This most likely occurs because of the relatively long carbon-bromine bond, the distorted ring geometry, and the relatively high polarizability …


Scaling Behavior Of Atomic Trajectories In Confined Fluids, Amy Lisa Graves, B. J. Berne Oct 1991

Scaling Behavior Of Atomic Trajectories In Confined Fluids, Amy Lisa Graves, B. J. Berne

Physics & Astronomy Faculty Works

We study the dependence of D, a quantity that has previously been associated with the fractal dimension of an atomic trajectory, on the scale on which it is measured. Single-particle and relative trajectories are generated by molecular-dynamics simulations of Lennard-Jones atoms permanently trapped in a spherical pore. Transient trapping is studied with a generalized Langevin model of dynamics. Confinement of trajectories allows D to exceed 2; in the case of permanent trapping, D diverges.


Internal Caustic Structure Of Illuminated Liquid Droplets, James A. Lock, Edward A. Hovenac Oct 1991

Internal Caustic Structure Of Illuminated Liquid Droplets, James A. Lock, Edward A. Hovenac

Physics Faculty Publications

The internal electric field of an illuminated liquid droplet is studied in detail with the use of both wave theory and ray theory. The internal field attains its maximum values on the caustics within the droplet. Ray theory is used to determine the equations of these caustics and the density of rays on them. The Debye-series expansion of the interior-field Mie amplitudes is used to calculate the wave-theory version of these caustics. The physical interpretation of the sources of stimulated Raman scattering and fluorescence emission within a liquid droplet is then given.


Structure, Morphology And Growth Of Biogenic Greigite (Fe3S4), Brigid R. Heywood, Stephen Mann, Richard B. Frankel Oct 1991

Structure, Morphology And Growth Of Biogenic Greigite (Fe3S4), Brigid R. Heywood, Stephen Mann, Richard B. Frankel

Physics

Several species of aquatic bacteria are known to exploit the earth's geomagnetic field as a means of directing their motion towards suitable habitats. A feature common to these bacteria is the presence of discrete intracellular magnetic inclusions, magnetosomes, aligned in chains along the long axis of the organism. The size and orientation of the individual magnetic particles imparts a permanent magnetic dipole moment to the cell which is, in turn, responsible for the magnetotactic response. In all species examined to date the magnetic particles have been found to be well-ordered, single domain, membrane-bounded crystals with reproducible, species-specific morphologies. Until recently, …


Inorganic Particles Produced By Microorganisms, Richard B. Frankel Oct 1991

Inorganic Particles Produced By Microorganisms, Richard B. Frankel

Physics

The processes by which microorganisms, particularly bacteria, produce inorganic mineral particles are reviewed.


Study Of Cathodoluminescence In Semiconductors, Mandakini V. Kale Oct 1991

Study Of Cathodoluminescence In Semiconductors, Mandakini V. Kale

Electrical & Computer Engineering Theses & Dissertations

Cathodoluminescence in Zn doped GaAs and ZnSe, the materials of interest for electron-beam controlled semiconductor switches, has been investigated. A new diagnostic technique, using telescopic setup of lenses, was developed to study the spatially resolved cathodoluminescence. The setup eliminated the light, other than rays from the sample, parallel to the optical axis, resulting in an enhanced spatial resolution. At high e-beam energies, light was detected, from the Zn layer region in the GaAs. It is proposed to be due to the radiative recombination of electron-hole pairs, created by the e-beam. For the polycrystalline ZnSe no light emission was detected. This …


Auxiliary Field In Conformal Gauge Theory, James Thomas Wheeler Sep 1991

Auxiliary Field In Conformal Gauge Theory, James Thomas Wheeler

All Physics Faculty Publications

When the full conformal algebra is gauged there arises a gauge field for inverse translations in addition to the usual translational gauge field. By considering every scale-invariant action constructible from the curvatures of the conformal group and the metric, we show that when the gauge field of the usual translations is identified as the vierbein, the gauge field of inverse translations may always be eliminated by its own field equation. After this elimination, every torsion-free, scale-invariant action reduces to a linear combination of the square of the conformal curvature tensor Cαβμν and the square of the Weyl field strength …