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Articles 32191 - 32220 of 36558

Full-Text Articles in Physical Sciences and Mathematics

Structure And Electrical Properties Of La1 - Xsrxco1 - Yfeyo3. Part 2. The System La1 - Xsrxco0.2fe0.8o3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin Jan 1995

Structure And Electrical Properties Of La1 - Xsrxco1 - Yfeyo3. Part 2. The System La1 - Xsrxco0.2fe0.8o3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin

Materials Science and Engineering Faculty Research & Creative Works

Crystal structure, thermal expansion, oxygen stoichiometry, thermoelectricity, and electrical conductivity of compositions in the system La1 - xSrxCo0.2Fe0.8O3 with 0 ≤ x ≤ 0.6 were studied as function of temperature and Sr content, in air. The solubility of Sr in the sintered perovskite-type oxide (ABO3) was limited to x ≤ 0.4. The observed p-type electrical conduction appeared to occur via a small-polaron hopping mechanism. The thermally induced oxygen loss caused a lattice expansion plus decreases in both the carrier concentration and the carrier mobility. A semi-empirical model was developed which takes into account the thermally activated disproportionation of Co3+ ions …

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The Light Ion Pulsed Power Induction Accelerator For Etf, Ronald E. Olson, M. G. Mazarakis, C. L. Olson, D. L. Smith, L. F. Bennett Jan 1995

The Light Ion Pulsed Power Induction Accelerator For Etf, Ronald E. Olson, M. G. Mazarakis, C. L. Olson, D. L. Smith, L. F. Bennett

Physics Faculty Research & Creative Works

The light ion Engineering Test Facility (ETF) driver concept, based on Hermes III and RHEPP technologies, is a scaled-down version of the LMF design incorporating repetition rate capabilities of up to 10 Hz. The preconceptual design presented here provides 250 TW peak power to the ETF target during 8 ns, equal to 2 MJ total ion beam energy. Linear inductive voltage addition driving a self-magnetically insulated transmission line (MITL) is utilized to generate the 36 MV peak voltage needed for lithium ion beams. The ~3 MA ion current is achieved by utilizing many accelerating modules in parallel. Since the current …

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Two-Body Photodisintegration Of The Deuteron Up To 2.8 Gev, J. E. Belz, D. H. Potterveld, S. E. Kuhn, J.F. J. Van Den Brand, J. L. White, B. Zeidman, Et Al. Jan 1995

Two-Body Photodisintegration Of The Deuteron Up To 2.8 Gev, J. E. Belz, D. H. Potterveld, S. E. Kuhn, J.F. J. Van Den Brand, J. L. White, B. Zeidman, Et Al.

Physics Faculty Publications

Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at θc.m. = 90° is in agreement with the constituent counting rules.

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Evidence For Virtual Compton Scattering From Proton, J.F.J. Van Den Brand, R. Ent, P. L. Anthony, R. G. Arnold, J. Arrington, E. J. Beise, J. E. Belz, P. E. Bosted, H. J. Bulten, M. S. Chapman, K. P. Coulter, F. S. Dietrich, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.-O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Makins, D.J. Margaziotis, R.D. Mckeown, R.G. Milner, B. Mueller, J. Napolitano, J. Nelson, T. G. O'Neill, V. Pavavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K Van Bibber, D. A. Wasson, J.L. White, B. Zeidman Jan 1995

Evidence For Virtual Compton Scattering From Proton, J.F.J. Van Den Brand, R. Ent, P. L. Anthony, R. G. Arnold, J. Arrington, E. J. Beise, J. E. Belz, P. E. Bosted, H. J. Bulten, M. S. Chapman, K. P. Coulter, F. S. Dietrich, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.-O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Makins, D.J. Margaziotis, R.D. Mckeown, R.G. Milner, B. Mueller, J. Napolitano, J. Nelson, T. G. O'Neill, V. Pavavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K Van Bibber, D. A. Wasson, J.L. White, B. Zeidman

Physics Faculty Publications

In virtual Compton scattering an electron is scattered off a nucleon such that the nucleon emits a photon. We show that these events can be selected experimentally, and present the first evidence for virtual Compton scattering from the proton in data obtained at the Stanford Linear Accelerator Center. The angular and energy dependence of the data is well described by a calculation that includes the coherent sum of electron and proton radiation.

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Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu Jan 1995

Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu

Electrical & Computer Engineering Faculty Publications

Scanning-tunneling microscopy has been used to study temperature and coverage dependence of the structure of lead on the Si(111)-7×7 surface. For low Pb coverage, the Pb atoms favored the faulted sites. The ratio between the number of Pb atoms on faulted to unfaulted sites increased after sample annealing. An energy difference of 0.05 eV associated with a Pb atom on these two sites is estimated. The mobility of Pb atoms on Si(111) was observed at a temperature as low as 260°C for a coverage of 0.1 and 1 ML. © 1995 The American Physical Society.

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Calculations Of The Interactions Of Energetic Ions With Materials For Protection Of Computer Memory And Biological Systems, Myung-Hee Y. Kim Jan 1995

Calculations Of The Interactions Of Energetic Ions With Materials For Protection Of Computer Memory And Biological Systems, Myung-Hee Y. Kim

Dissertations, Theses, and Masters Projects

Theoretical calculations were performed for the propagation and interactions of particles having high atomic numbers and energy through diverse shield materials including polymeric materials and epoxy-bound lunar regolith by using transport codes for laboratory ion beams and the cosmic ray spectrum. Heavy ions fragment and lose energy upon interactions with shielding materials of specified elemental composition, density, and thickness. A fragmenting heavy iron ion produces hundreds of isotopes during nuclear reactions, which are treated in the solution of the transport problem used here. A reduced set of 80 isotopes is sufficient to represent the charge distribution, but a minimum of …

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A Delta-F Monte Carlo Method To Calculate Parameters In Plasmas, Maciek Sasinowski Jan 1995

A Delta-F Monte Carlo Method To Calculate Parameters In Plasmas, Maciek Sasinowski

Dissertations, Theses, and Masters Projects

A Monte Carlo code has been developed which very efficiently calculates plasma parameters, such as currents, potentials and transport coefficients for a fully three dimensional magnetic field configuration. The code computes the deviation, f, of the exact distribution function, f, from the Maxwellian, {dollar}F\sb{lcub}M{rcub},{dollar} with {dollar}\psi{dollar} the toroidal magnetic flux enclosed by a pressure surface and H the Hamiltonian. The particles in the simulation are followed with a traditional Monte Carlo scheme consisting of an orbit step in which new values for the positions and momenta are obtained and a collision step in which a Monte Carlo equivalent of the …

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First Principles Linear Response Calculations Of Lattice Dynamics, Cheng-Zhang Wang Jan 1995

First Principles Linear Response Calculations Of Lattice Dynamics, Cheng-Zhang Wang

Dissertations, Theses, and Masters Projects

First principles calculations, using the density-functional theory and particularly the local density approximation (LDA), have achieved remarkable success in studying the properties of solid state systems. Although the basic results of these calculations are the electronic structures (eigenvalues, eigenfunctions, etc.) and the total energy of ground state, many other related physical properties can be deduced from them by investigating their response under external perturbations. Using the linear response method with linearized-augmented-plane-wave (LAPW) basis, we have calculated lattice dynamical properties of important semiconductors CuCl, SiC and ferroelectric KNbO{dollar}\sb3.{dollar} CuCl is known to exhibit large anharmonic effects and possibly a complicated multi-well …

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Young's Double-Slit Interferometry Within An Atom, Michael W. Noel, C. R. Stroud Jr. Jan 1995

Young's Double-Slit Interferometry Within An Atom, Michael W. Noel, C. R. Stroud Jr.

Physics Faculty Research and Scholarship

An experiment is described which is an analog of Young's double-slit interferometer using an atomic electron instead of light. Two phase-coherent laser pulses are used to excite a single electron into a state of the form of a pair of Rydberg wave packets that are initially on opposite sides of the orbit. The two wave packets propagate and spread until they completely overlap, then a third phase-coherent laser pulse probes the resulting fringe pattern. The relative phase of the two wave packets is varied so that the interference produces a single localized electron wave packet on one side of the …

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Solid State Proton Spin Relaxation And Methyl Reorientation In Isopropylbenzene, Amy L. Plofker, Peter A. Beckmann Jan 1995

Solid State Proton Spin Relaxation And Methyl Reorientation In Isopropylbenzene, Amy L. Plofker, Peter A. Beckmann

Physics Faculty Research and Scholarship

No abstract provided.

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Electrical Characterization Of The (La,Ca) (Cr,Co)O3 System, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin Jan 1995

Electrical Characterization Of The (La,Ca) (Cr,Co)O3 System, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

The results of electrical conductivity and thermopower measurements are presented for selected (La,Ca)(Cr,Co)O3 compositions. The La1 - xCaxCrO3 compounds are typical p-type small polaron conductors. The La1 - xCaxCrO3 compounds are found to be small polaron conductors at room temperature for x ≤ 0.20 with a higher electrical conductivity than the corresponding chromite's. The electrical conductivity at room temperature is lower for Co-rich compositions than for Cr-rich compositions for compositions containing 10 mol% and 20 mol% Ca. This fact is attributed to the trapping of p-type small polarons at energetically lower Cr sites, resulting in a broad room temperature conductivity …

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The Massive Multi - Flavor Schwinger Model, James E. Hetrick, Y. Hosotani, S. Iso Jan 1995

The Massive Multi - Flavor Schwinger Model, James E. Hetrick, Y. Hosotani, S. Iso

All Faculty Articles - School of Engineering and Computer Science

Non-perturbatively generated effective potentials play an extremely useful and often critical role in string and inflationary model building. These potentials are typically computed by methods that assume the system is in equilibrium. For systems out of equilibrium, like an inflaton rolling down its potential, there are corrections to the semi-classical evolution due to transient phenomena. We provide a new qualitative and quantitative understanding of non-perturbative effects in real time for a wide class of toy quantum mechanical models. We derive an effective Schrödinger equation that does not rely on any notion of equilibrium and captures the low-energy dynamics supposedly described …

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Effects Of Large Aspect Ratios And Fluctuations On Hard X-Ray-Detection In Lower Hybrid Driven Divertor Tokamaks, Linda L. Vahala, George Vahala, Paul Bonoli Jan 1995

Effects Of Large Aspect Ratios And Fluctuations On Hard X-Ray-Detection In Lower Hybrid Driven Divertor Tokamaks, Linda L. Vahala, George Vahala, Paul Bonoli

Electrical & Computer Engineering Faculty Publications

It is shown that lower hybrid wave scattering from fluctuations plays a critical role in large aspect ratio divertor plasmas even through the edge density fluctuation levels are only at 1%. This is seen in the theoretically calculated electron power-density profiles which can be directly correlated to the standard experimental chordal hard x-ray profiles. It thus seems that fluctuation effects must be included in determining rf current-density profiles.

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Justifying A Search For A Unifying Theory Of Unconstitutional Conditions, Roberto L. Corrada Jan 1995

Justifying A Search For A Unifying Theory Of Unconstitutional Conditions, Roberto L. Corrada

Sturm College of Law: Faculty Scholarship

This essay explores why many scholars, including Frederick Schauer and Larry Alexander, feel that an attempt at unification of the doctrine of unconstitutional conditions is unworthy of scholarly attention. Although the subject of this particular essay is less ambitious than the many attempts that have been made to unify the doctrine of unconstitutional conditions, and indeed proposes no unifying theory itself, it nevertheless examines why attempts to explain the doctrine in a unified way might be valid even if no unification is ultimately possible. It also attempts to persuade that a unifying theory of the doctrine may be attainable, although …

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Fermi Problems: Educated Guesses, John A. Adam Jan 1995

Fermi Problems: Educated Guesses, John A. Adam

Mathematics & Statistics Faculty Publications

No abstract provided.

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The Characterization Of The Radiative Energy Transfer Process Among Holmium(3+) Ions In Yttrium(3) Aluminum(5) Oxygen(12), Terri Lynn Lazarus Jan 1995

The Characterization Of The Radiative Energy Transfer Process Among Holmium(3+) Ions In Yttrium(3) Aluminum(5) Oxygen(12), Terri Lynn Lazarus

Dissertations, Theses, and Masters Projects

This research comprises a comprehensive spectroscopic study of the characteristics of the solid state crystal YAG (Yttrium Aluminum Garnet) singly doped with Ho (Holmium) ions. An important area of solid state laser crystal research is the determination and optimization of the processes within these laser crystals which lead to efficient laser action. In most laser crystals, there is a donor ion such as Tm (Thulium) and an acceptor ion such as Ho. The donor ion generally has greater absorption than that of the acceptor at the wavelength of the pump source. The donor ion can transfer this absorbed energy to …

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Search For Metastability Of 2s Muonic Neon, Bernard Wilhelm Bach Jan 1995

Search For Metastability Of 2s Muonic Neon, Bernard Wilhelm Bach

Dissertations, Theses, and Masters Projects

An experiment was performed at the Paul Scherrer Institut (PSI) to establish the conditions for the metastability of the 2S-state of muonic neon. The muonic atoms were formed by stopping negative muons in the neon-filled target chamber of the PSI cyclotron trap. A pair of intrinsic germanium detectors were used in coincidence to search for the two photon decay of the 2S-state. Both energy and time information from two photon events were written to disk for off-line analysis. Data were accumulated for neon pressures of 40 and 400 Torr. The data were then searched for evidence of two photon transitions …

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Beam Dynamics In The Cebaf Superconducting Cavities, Zenghai Li Jan 1995

Beam Dynamics In The Cebaf Superconducting Cavities, Zenghai Li

Dissertations, Theses, and Masters Projects

This work is a study of beam dynamics in the CEBAF superconducting cavities under the influence of the fields generated by externally applied RF and beam particles.;A full 3-D modeling of the CEBAF 5-cell superconducting cavity is carried out. Details of the modeling with MAFIA are discussed. Multipole fields due to the asymmetric couplers are studied by means of 3-D Fourier transforms. The cavity steering and focusing of the multipole fields are studied. Experimental measurements of these effects are performed to validate the modeling. Evaluation of the cavity misalignment is discussed. The emittance degradation effects in the CEBAF superconducting linacs …

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Radio-Frequency Superconducting Parametric Transducer For Gravitational-Wave Antennae, M. A. Fisher, Mark F. Bocko, Linda E. Marchese, Guizhen Zhang, Munawar Karim Jan 1995

Radio-Frequency Superconducting Parametric Transducer For Gravitational-Wave Antennae, M. A. Fisher, Mark F. Bocko, Linda E. Marchese, Guizhen Zhang, Munawar Karim

Physics Faculty/Staff Publications

We report on the design and testing of an ultrasensitive, electromechanical transducer for use on resonant mass gravitational wave antennae. The transducer is a superconducting, radio frequency resonant bridge circuit operating near 200 MHz. We have minimized several important sources of noise in this transducer system. The Johnson noise of the transducer circuit is reduced through using a superconducting niobium stripline circuit and low‐loss insulating materials. At a temperature of 4.2 K we have achieved unloaded electrical quality factors of 200 000. The bridge circuit is balanced by piezoelectric actuators which control the spacing between the proof mass and capacitive …

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Mcplib: A Collection Of Nonlinear Mixed Complementarity Problems, Steven P. Dirkse, Michael C. Ferris Jan 1995

Mcplib: A Collection Of Nonlinear Mixed Complementarity Problems, Steven P. Dirkse, Michael C. Ferris

University Faculty Publications and Creative Works

The origins and some motivational details of a collection of nonlinear mixed complementarity problems are given. This collection serves two purposes. Firstly, it gives a uniform basis for testing currently available and new algorithms for mixed complementarity problems. Function and Jacobian evaluations for the resulting problems are provided via a GAMS interface, making thorough testing of algorithms on practical complementarity problems possible. Secondly, it gives examples of how to formulate many popular problem formats as mixed complementarity problems and how to describe the resulting problems in GAMS format. We demonstrate the ease and power of formulating practical models in the …

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Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler Jan 1995

Xenon 147-Nm Resonance Ƒ Value And Trapped Decay Rates, H. M. Anderson, Scott D. Bergeson, D. A. Doughty, J. E. Lawler

Faculty Publications

The absorption oscillator strength of the xenon 147-nm resonance transition is measured to be 0.264±0.016. This value is from direct absorption measurements with equivalent widths from ≈ 1 to ≈ 10 cm-1. This ƒ-value measurement is compared to others in the literature and is used in Monte Carlo simulations of trapped decay rates. The simulations include an angle-dependent partial frequency redistribution. The simulation results are compared to trapped decay rates in the literature.

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Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd Jan 1995

Waterjet Cutting Of Cross-Linked Glass, Fang Yuan, John A. Johnson, David D. Allred, Robert H. Todd

Faculty Publications

The cutting of cross-linked glasses such as silica and Corning 7059 can be difficult. We conducted an experimental study to determine the feasibility of using a high-speed waterjet to cut thin Corning 7095 glass. Cutting using either pure de-ionized high pressure water at 380 MPa (55 000 psi) or de-ionized water with entrained garnet abrasive was studied. The roughness of the cut surfaces was measured and compared. Photomicrographs were taken of glass examples cut at different traversing rates with pure water and with the abrasive entrained waterjet. Comparative studies of cutting with and without the entrained abrasive material showed that …

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Density Of States Of A Damped Quantum Oscillator, Andreas Hanke, W. Zwerger Jan 1995

Density Of States Of A Damped Quantum Oscillator, Andreas Hanke, W. Zwerger

Physics and Astronomy Faculty Publications and Presentations

We calculate the density of states of a damped quantum-mechanical harmonic oscillator which is described by a Caldeira-Leggett type model with Ohmic dissipation and a Drude-like cutoff. From the exact expression for the associated partition function, we derive the asymptotic behavior of the density of states using Tauberian theorems. An effective algorithm to evaluate the density of states is presented and examples are given. It is pointed out that the calculated density of states is an experimentally accessible quantity.

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Applicability Of Bispectral Analysis To Unstable Plasma Waves, Renaud Stauber Jan 1995

Applicability Of Bispectral Analysis To Unstable Plasma Waves, Renaud Stauber

Graduate Theses, Dissertations, and Problem Reports

A program to implement a spectral analysis technique called the bispectrum was written and tested with computer generated time series data. The application of the algorithm to the study of nonlinear interactions was demonstrated by a comparison of computed quantities with results from model equations found in the literature. Specifically determined were: the amplitude and phase of coupling coefficients, the power transfer function, the fraction of power associated with nonlinear coupling, and the identification of waves involved in a quadratic coupling interaction. A method of distinguishing the two parent waves from the daughter wave in this three-wave interaction is proposed …

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Theoretical Investigation Of Two-Color, Two-Photon, 6s(2)S(1/2) → 5d(2)D(J) → 11p(2)P(3/2) Excitation And Depolarization Spectra In Atomic Cesium, Boris Dobrydnev Jan 1995

Theoretical Investigation Of Two-Color, Two-Photon, 6s(2)S(1/2) → 5d(2)D(J) → 11p(2)P(3/2) Excitation And Depolarization Spectra In Atomic Cesium, Boris Dobrydnev

Physics Theses & Dissertations

The theoretical investigation of two-photon, two-color intensity and depolarization spectra for the 6s2S1/2 → 5d2Dj → 11p2P3/2 transition in atomic caesium is considered. For quadrupole-dipole transitions the dependence of excitation from the ratio of reduced matrix elements is shown. The experimental method of determination of the value and sign of the ratio is proposed. Comparison of results for co- and counterpropagating beams revealed the strong dependence of the transition rate on the relative beam directions. Analysis of the influence of the external electric field on the process of absorption is presented. …

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Precision Measurement Of Relative Dipole Matrix Elements In Atomic Sodium, Rodney P. Meyer Jan 1995

Precision Measurement Of Relative Dipole Matrix Elements In Atomic Sodium, Rodney P. Meyer

Physics Theses & Dissertations

Relative dipole matrix elements are measured by means of a new spectroscopic technique called polarization interference spectroscopy. It is a two-color two-photon nonresonant process that maps the matrix elements into the energy domain by means of quantum mechanical interference. The technique measures the relative magnitude of the reduced matrix elements, particularly those involving excited states, to accuracies that are an order of magnitude better than previously available. Also, for the first time the relative phase of the reduced matrix elements is measured. The ratio of reduced matrix elements for the transitions 3s 2S1/2 →3P 2P3/2 →5s …

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Compensation And Characterization Of Gallium Arsenide, Randy A. Roush Jan 1995

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush

Electrical & Computer Engineering Theses & Dissertations

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow …

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Quark Masses And Binding-Energy In A Proton - Answer To Question Number-2a, Br Holstein Dec 1994

Quark Masses And Binding-Energy In A Proton - Answer To Question Number-2a, Br Holstein

Barry R Holstein

No abstract provided.

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Determination Of Plasma Parameters In A Dc Arcjet Part Ii, Scott Reeve, Wayne Weimer Dec 1994

Determination Of Plasma Parameters In A Dc Arcjet Part Ii, Scott Reeve, Wayne Weimer

Scott Reeve

No abstract provided.

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Critical Dynamics Of Nonconserved Ising-Like Systems, K. E. Bassler, Beate Schmittmann Dec 1994

Critical Dynamics Of Nonconserved Ising-Like Systems, K. E. Bassler, Beate Schmittmann

Beate Schmittmann

We show that the dynamical fixed point of Ising-like models, characterized by a single scalar, nonconserved ordering field, is stable near four dimensions with respect to all dynamic perturbations, including those of a nonequilibrium nature.

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