Physical Sciences and Mathematics Commons^™

A Generalized Molien Function For Field Theoretical Hamiltonians, Jeffrey W. Felix, Dorian M. Hatch

Faculty Publications

A generating function, or Molien function, the coefficients of which give the number of independent polynomial invariants in G, has been useful in the Landau and renormalization group theories of phase transitions. Here a generalized Molien function for a field theoretical Hamiltonian (with short-range interactions) of the most general form invariant in a group G is derived. This form is useful for more general renormalization group calculations. Its Taylor series is calculated to low order for the FGamma-2 representation of the space group R[3 bar]c and also for the l=1 (faithful) representation of SO(3).

Minimal Norm Constrained Interpolation, Larry Dean Irvine

Mathematics & Statistics Theses & Dissertations

In computational fluid dynamics and in CAD/CAM a physical boundary, usually known only discreetly (say, from a set of measurements), must often be approximated. An acceptable approximation must, of course, preserve the salient features of the data (convexity, concavity, etc.) In this dissertation we compute a smooth interpolant which is locally convex where the data are locally convex and is locally concave where the data are locally concave.

Such an interpolant is found by posing and solving a minimization problem. The solution is a piecewise cubic polynomial. We actually solve this problem indirectly by using the Peano kernel theorem to …

Mossbauer Study Of Gadolinium Iron Garnet, Jun Li

Physics Theses & Dissertations

The Mossbauer spectroscopic study of Gadolinium Iron Garnet R₃Fe5^O12 (GdIG) has been performed over the temperature range of 7K to 715K. Both high temperature and low temperature properties of GdIG have been studied. The magnetization is along (111) direction over this temperature range. The internal magnetic fields at Fe⁵⁷ sites in GdIG gave two values for the octahedral(a), site which differ by 4-6 KOe and one value for the tetrahedral (d), site at each temperature. Measurements of the total isomer shift in the spectra show that the shift of the center of the spectra consists …

Observation Of H/E Aharonov-Bohm Oscillations In Normal-Metal Rings, Richard A. Webb, S. Washburn, C. P. Umbach, R. B. Laibowitz

Faculty Publications

Magnetoresistance oscillations periodic with respect to the flux h/e have been observed in submicron-diameter Au rings, along with weaker h/2e oscillations. The h/e oscillations persist to very large magnetic fields. The background structure in the magnetoresistance was not symmetric about zero field. The temperature dependence of both the amplitude of the oscillations and the background are consistent with the recent theory by Stone.

Effects Of Dissipation And Temperature On Macroscopic Quantum Tunneling, S. Washburn, Richard A. Webb, R. F. Voss, S. M. Faris

Faculty Publications

Measurements of the tunneling rate Γ out of the zero-voltage state for several Nb edge junctions with differing shunt capacitances are described. At zero temperature, increasing the shunt capacitance lowers Γ in agreement with dissipative calculations of the macroscopic-quantum-tunneling rate. As temperature increases, ln[Γ(T)/Γ(0)]∝T² as recently predicted.

Copper Electrodeposition In A Magnetic Field, Hiroshi Takeo

Dissertations and Theses

The effect of a magnetic field on copper electrodeposition was investigated. Copper was electrodeposited onto square copper cathodes 1 sq cm in area from an aqueous solution (0.5 M CuSO₄, 0.5 M H₂SO₄. A glass cell was placed between the pole pieces of an electromagnet, and the magnetic fields applied were in the range from 0 to 12.5 kG. The current density was in the range from 80 mA/sq cm to 880 mA/sq cm. In each of the experiments, cell current, cell voltage, and cell temperature were monitored with a microcomputer. The weight …

Crystalline And Amorphous Feti And Fe2Ti, C.L. Chien, Sy_Hwang Liou

Sy-Hwang Liou Publications

Amorphous FeTi, Fe₂Ti, and their crystalline counterparts are compared by measurements of x-ray diffraction, conductivity, and ⁵⁷Fe Mössbauer spectroscopy. In FeTi one has the unique opportunity to compare a cubic crystal with its amorphous analog. X-ray diffraction and hyperfine interactions indicate no clear correlation between the crystalline and the amorphous states. The electrical conductivity exhibits distinctive behavior for the two states.

Reduction Of Mammalian Ferritin, G. D. Watt, Richard B. Frankel, G. C. Papaefthymiou

Physics

Mammalian ferritin from horse spleen undergoes an electrochemical or chemical reduction reaction in which each iron atom present is reduced by one electron (2300 electrons per ferritin molecule containing 2300 Fe³⁺ ions). Midpoint potentials of -190 mV, -310 mV, and -416 mV were determined at pH 7.0, 8.0, and 9.0. This variation of potential with pH indicates that ≈ 2 H⁺ are transferred to the core for each Fe³⁺ reduced to Fe²⁺. Mössbauer measurements of partially reduced ferritin give spectra that consist of a ferric quadrupole doublet with a superposed ferrous quadrupole doublet. The relative …

N-Color Spin Models In The Large N Limit, Mehran Kardar, Miron Kaufman

Miron Kaufman

N color spin models are introduced and examined in the large N limit. The free energy and critical properties at the phase transition are studied. With relevant couplings between colors the transition becomes either first order or Fisher renormalized. With irrelevant couplings there is a crossover to first-order transitions through a nonclassical tricritical point. Connections are established between the N-color model, compressible systems, and systems with random impurities.

First-Principles Study Of Structural Instabilities In Halide-Based Perovskites: Competition Between Ferroelectricity And Ferroelasticity, J. W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer

John R. Hardy Papers

We have made a systematic theoretical survey of the competition between ferroelastic and ferroelectric instabilities in the family of halide-based perovskites of formula ABX₃, where A is an alkali-metal ion, B is a Be, Mg, or Ca ion, and X is a halide ion. Initially we surveyed the whole series of such compounds, making a theoretical lattice-dynamical study using first-principles interionic potentials composed of a long-range pure Coulomb interaction between the spherically symmetric free ions, and a short-range component calculated by the Gordon-Kim approach from the overlapping free-ion charge densities. We then proceeded to examine in more detail …

First-Principles Study Of Structural Instabilities In Halide-Based Perovskites: Competition Between Ferroelectricity And Ferroelasticity, John W. Flocken, R. A. Guenther, John R. Hardy, L. L. Boyer

Physics Faculty Publications

We have made a systematic theoretical survey of the competition between ferroelastic and ferroelectric instabilities in the family of halide-based perovskites of formula ABX3, where A is an alkali-metal ion, B is a Be, Mg, or Ca ion, and X is a halide ion. Initially we surveyed the whole series of such compounds, making a theoretical lattice-dynamical study using first-principles interionic potentials composed of a long-range pure Coulomb interaction between the spherically symmetric free ions, and a short-range component calculated by the Gordon-Kim approach from the overlapping free-ion charge densities. We then proceeded to examine in more detail three compounds, …

Confinement Of Electron Orbits And The Interaction Between The Electron Beam And Cavity Modes In The Orbitron Maser, Wlodzimierz Nakonieczny

Doctoral Dissertations

The Orbitron maser, developed over recent years in the University of Tennessee Plasma Laboratory, is an alternative microwave source, capable of producing microwave radiation up to the submillimeter range. It operates on the basis of interaction between an electrostatically confined electron cloud and electromagnetic field in the Orbitron resonator. Good confinement of the cloud is very important for an efficient operation of the Orbitron, and is directly related to the shape of electron orbits in the device. It appears that the radial confinement can be determined by two simple criteria concerning the electron's angular momentum L and energy E. The …

Relativistic Plasma-Wave Excitation By Collinear Optical Mixing, C.E. Clayton, C. Joshi, C. Darrow, Donald P. Umstadter

Donald Umstadter Publications

The relativistic plasma wave excited when the frequency difference between two copropagating CO₂ laser beams equals the plasma frequency is detected for the first time. The plasma-wave frequency, wave number, spatial extent, and saturation time are directly measured by use of 7-mrad, collective, ruby Thomson scattering and the forward-scattered ir spectrum. The wave amplitude ñ/n₀ is inferred to be (1-3)% which gives a longitudinal electric field of 0.3 to 1 GV/m at a laser intensity of 1.7×10¹³ W/cm², in reasonable agreement with theory.

Kl−Ks Mass Difference And Supersymmetric Left-Right-Symmetric Theories, Asim Gangopadhyaya

Physics: Faculty Publications and Other Works

The supersymmetric contributions to the K_L−K_S mass difference makes the previously obtained bounds on the right-handed scale (M_R>1.6 TeV) much weaker. This raises the interesting possibility that the left-right model could be tested as an alternative to SU_L(2)⊗U(1) at low energies. Also we find that to demand that the supersymmetric contribution to the K_L−K_S mass difference be less than 3.5×10⁻¹⁵ GeV requires that scalar-quark masses be more than 400 GeV.

Determining The Temperature-Dependent Characteristic Temperature Of Beryllium From Electrical Resistance Measurements, Thomas W. Listerman, Xiao-Li Zhou

Thomas Listerman

We have developed an intermediate-level laboratory experiment to determine the temperature- dependent characteristic temperature of beryllium. The apparatus used to measure the resistance of a beryllium wire sample between liquid nitrogen and room temperatures was simple. The characteristic temperatures obtained from these data using the Block-Grüneisen model are in reasonable agreement with literature values obtained from resistivity and heat capacity experiments. The experiment introduced students to cryogenic and computer data analysis techniques and forced them to extend their knowledge of the theory of electrical resistance and of characteristic temperatures.

Experimental Study Of Spin-Exchange Effects In Elastic And Ionizing Collisions Of Polarized Electrons With Polarized Hydrogen Atoms, G. D. Fletcher, M. J. Alguard, Timothy J. Gay, V. W. Hughes, P.F. Wainwright, M. S. Lubell, W. Raith

Timothy J. Gay Publications

Using crossed beams of polarized electrons and polarized hydrogen atoms we have investigated the effect of spin exchange on 90° elastic scattering from 4.4 to 30.3 eV and impact ionization from 14.1 to 197.0 eV. Our results suggest that the range of validity of various theoretical approximation methods is more restricted than had been assumed previously.

Analysis Of A Rocket-Borne Resonant Scatter System For Measurement Of Atomic Oxygen, Neil B. Myers

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A computer model has been developed at Utah State University for interpreting the results of a rocket-borne resonant scatter measurement system using 1304 A radiation. Atomic oxygen densities are obtained from 65 to 140 km from three rocket flights. The resolution of the system is < 0.1 km, and considerable structure has been observed. The variety of shapes exhibited by the three profiles suggest a dynamic nature to atomic oxygen density profiles in the lower ionosphere. Maximum densities between 2.6 x 10¹¹ and 1.2 x 10¹² cm^-3 were observed at altitudes between 92 and 95 km.

Measuring R And D Productivity, Richard A. Pappas, Donald S. Remer

All HMC Faculty Publications and Research

Measuring the productivity of an R&D organization is extremely tricky. Productivity is usually defined as a ratio of an output, like number of cars produced on an assembly line, to an input, like the wages paid the workers. While R&D may have a measurable input, the output is often intangible and difficult to quantify. This is further complicated because the return from an R&D department may not be realized for one or two decades,which means the time lag is much higher than in factory measurements. Furthermore, many researchers believe that this kind of measurement may be counterproductive,since the mere act …

Applications Of A Direct Fast Field/Reflectivity Method To Wave Propagation Modeling In Underwater Acoustic And Solid Earth Seismic Environments, Gerard Joseph Tango

University of New Orleans Theses and Dissertations

A new method is discussed for exact rapid computation of the depth-dependent Green's function occuring in full integral solutions to the acoustic and elastic Helmholtz wave equation, allowing calculations of underwater acoustic propagation loss and full wavefield synthetic seismograms, in range-independent plane stratified media.

Feasibility Studies Of Conversion Electron Mossbauer Spectroscopy (Cems) Of Iron-Doped Inp, Edward Agyekum

Physics Theses & Dissertations

An electron detector for conversion electron Mossbauer spectroscopy (CEMS) has been designed and built. Tests have been performed to study the effects on the electron detector resolution with respect to high anode voltage, He/CH₄ gas flow rate, and counting rate. These parameters have been optimized to detect the 7.3 keV conversion electrons emitted following resonant absorption of the 14.4 keV source gamma-rays associated with the Mossbauer effect using ⁵⁷Fe nuclei. CEMS spectra have been obtained using standard ⁵⁷Fe enriched and natural iron samples. CEMS spectra and Mossbauer transmission spectra have also been obtained for iron-compensated InP (InP:Fe) …

Beyond The Rigid-Ion Approximation With Spherically Symmetric Ions, L. L. Boyer, M. J. Mehl, J. L. Feldman, John R. Hardy, J. W. Flocken, C. Y. Fong

John R. Hardy Papers

Ab initio calculations show that a spherically symmetric charge relaxation of ions in a crystal, in response to the long-range electrostatic potential, is important for understanding the splitting between longitudinal- and transverse-optic-mode frequencies, and the violation of the Cauchy relations among elastic constants.

Beyond The Rigid-Ion Approximation With Spherically Symmetric Ions, L. L. Boyer, M. J. Mehl, J. L. Feldman, John R. Hardy, C. Y. Fong

Physics Faculty Publications

Ab initio calculations show that a spherically symmetric charge relaxation of ions in a crystal, in response to the long-range electrostatic potential, is important for understanding the splitting between longitudinal- and transverse-optic-mode frequencies, and the violation of the Cauchy relations among elastic constants.

Spin-Glass And Double-Transition Behavior In Gd-La Glasses, Michael J. O'Shea, David J. Sellmyer

David Sellmyer Publications

We report studies of high-field magnetization, field-cooled magnetization, thermoremanent magnetization, and isothermal remanent magnetization as a function of temperature in the metallic glass sytem Gd_xLa_72-xG₂₈ where G₂₈=Ga₁₈B₁₀ for the compositions x=72, 68, 64. The first two compositions show double-transition behavior and the last one shows only a paramagnetic to spin-glass transition. The approach to saturation at intermediate fields (up to 40 kOe) is of the form 1/H^1/2 as predicted by a mean field model which incorporates a small random anisotropy. The field-cooled magnetization in these samples is …

Random Magnetism In Amorphous Rare-Earth Alloys (Invited), David J. Sellmyer, S. Nafis

David Sellmyer Publications

Several aspects of the magnetic transitions seen in rare-earth metallic glasses are discussed, particularly with reference to recent theoretical work. These include: (a) apparent double transitions observed in Gd glasses where exchange fluctuations are important, (b) evidence for a correlated speromagnetic state recently predicted by Chudnovsky and Serota, and (c) the analysis of a Tb glass with strong random anisotropy in terms of an Ising-type spin-glass transition. Journal of Applied Physics is copyrighted by The American Institute of Physics.

Constraint On The Optical Constants Of A Film-Substrate System For Operation As An External-Reflection Retarder At A Given Angle Of Incidence, R. M.A. Azzam, Bruce E. Perilloux

Electrical Engineering Faculty Publications

Given a transparent film of refractive index n₁ on an absorbing substrate of complex refractive indexn₂-jk₂, we examine the constraint on n₁, n₂, and k₂ such that the film-substrate system acts as an external-reflection retarder of specified retardance Δ at a specified angle of incidence φ. The constraint, which takes the form ƒ(n₁,n₂,k₂;φ,Δ) = 0, is portrayed graphically by equi-n₁ contours in the n₂,k₂ plane at φ = 45, 70° and for Δ …

Anomalous Magnetic Hysteresis In An Amorphous Nd54Co36B10 Alloy, George C. Hadjipanayis, S.H. Aly, David J. Sellmyer

David Sellmyer Publications

The hysteresis and crystallization behavior of an amorphous Nd₅₄Co₃₆B₁₀ alloy have been examined over a range of temperatures. Crystallization studies show a glass transition temperature around 210 °C, two crystallization peaks at around 220 and 360 °C, and two endothermic peaks at around 530 and 600 °C, respectively. ac susceptibility measurements show an ordering temperature of 38 K for the amorphous phase. Four additional magnetic phases have been observed in the crystallized samples with ordering temperatures 17, 45, 90, and 190 K, respectively. Magnetic measurements on melt-spun ribbons reveal a coercivity of 6 kOe at …

Rapidly Quenched FeXTa100-X Alloys, C.L. Chien, Sy_Hwang Liou, B.K. Ha, K.M. Unruh

Sy-Hwang Liou Publications

Binary alloys of Fe_xTa_100-x were made by high-rate sputtering. A sharply defined boundary separates the composition ranges in which crystalline alloys (93 ≤ x ≤100) and amorphous alloys (15 ≤ x ≤ 90) are formed. The amorphous alloys with Fe concentrations up to the threshold of x_c ≈ 65 are nonmagnetic. For the samples with x > x_c, the magnetic ordering temperature (T_c) varies monotonically with Fe content to 200 K for a-Fe₉₀Ta₁₀. However, the crystalline alloys, with slightly higher Fe content, are strongly ferromagnetic. Their T …

Magnetic Properties And Hyperfine Interactions Of Amorphous Fe-Hf Alloys, Sy_Hwang Liou, G. Xiao, J.N. Taylor, C.L. Chien

Sy-Hwang Liou Publications

Alloys of Fe_xHf_100-x (20 ≤ x ≤ 100) were fabricated by a vapor-quench method. The amorphous state, as verified by x-ray diffraction, is realized over a wide composition range of 20 ≤ x ≤ 94. The magnetic phase diagram was determined. The variation with Fe content of the magnetic ordering temperature (T_{c) in Fe-Hf amorphous alloys shows a maximum at xp≈87. In contrast, the effective magnetic hyperfine field and therefore the Fe moment increases monotonically with x. Amorphous pure Fe is likely to be magnetic (Tc ~200 K) with …}

Origin Of The Peaked Structure In The Conductance Of One-Dimensional Silicon Accumulation Layers, Richard A. Webb, A. Hartstein, J. J. Wainer, A. B. Fowler

Faculty Publications

We have made extensive studies of the temperature, gate voltage, and electric field dependences of the conductance peaks in small silicon inversion layers in order to distinguish between resonant-tunneling models and a hopping model. We find that many of the peaks are consistent only with a hopping model, whereas some could be consistent with an early resonant-tunneling model. None of our structure is consistent with resonant tunneling if the recent formulation of Stone and Lee is correct.

Construction And Testing Of A New Atomic Physics Beam Line At The Western Michigan University Accelerator Laboratory, William Andrew Hollerman

Masters Theses

A new beam line containing a differentially-pumped gas cell and charge state analyzing magnet was constructed for the purpose of measuring a wide variety of atomic inner-shell processes, such as excitation, ionization, and charge transfer. The completed system will be able to measure these individual atomic processes using coincidence techniques. Initial testing of the beam line was performed using 40MeV S⁺⁷+Ar collisions to determine the effect of the collimating slit size on the measured x-ray cross sections. These measurements showed that the slip size on the measured x-ray cross sections. These measurements showed that the slit size affects …