Digital Commons Network^™

Self-Consistent Effective Binary Diffusion In Multicomponent Gas Mixtures, John D. Ramshaw

Physics Faculty Publications and Presentations

The correct treatment of diffusion in multicomponent gas mixtures requires solution of a linear system of equations for the diffusive mass fluxes relative to the mass-averaged velocity of the mixture. Effective binary diffusion approximations are often used to avoid solving this system. These approximations are generally internally inconsistent in the sense that the approximate diffusion fluxes do not properly sum to zero. The origin of this inconsistency is identified, and a general procedure for removing it is presented. This procedure applies equally to concentration, forced, pressure, and thermal diffusion, either separately or in combination. It is used to obtain a …

The Effects Of Prisms Learning Cycle Strategies On Achievement, Integrated Process Skills, And Attitudes Towards Physics Of High School Physics Students When Referenced To Kolb’S Learning Style Inventory, Michael P. Kelly

Dissertations and Theses @ UNI

This study asked the question: Is the gain in physics achievement, process skills, and attitudes toward physics, using the PRISMS teaching strategy, different among high school physics students in the four cognitive learning modes identified by the Kolb Learning Styles Inventory (LSI)? In this study a group of high school physics students were tested for gains in scores in the three areas mentioned in the statement of the problem. This treatment group was taught using PRISMS teaching strategies. Their learning styles were classified according to the Kolb LSI. The procedure followed for this study included administration of the Kolb LSI …

Calculation Of Electron Scattering For 4He In A Continuum Shell Model, Ming Yu

Masters Theses

Calculations for the electroexcitation of the ⁴He, O+ state have been performed within the context of recoil corrected continuum shell model. Approximations previously employed for inelastic scattering with the recoil corrected continuum shell model are eliminated in the work. The O+ state exhausts only 10% of the energy weighted sum rule and previous shell model calculations for the excitation of this state produce about ten times too much strength. This difficulty is alleviated by the use translationally invariant wave functions and the application of continuum boundary conditions for this particle unbound state. The structure of the O+ state is …

Relativistic And Non-Relativistic Nuclear Charge Form Factors, Tao Wang

Masters Theses

This thesis presents an examination that the two nuclear charge form factors, relativistic and non-relativistic, are equivalent approximately in an appreciable range. The relativistic one is contributed by both vector charge density and tensor charge density. And the non-relativistic charge form factor is contributed by the nuclear densities from experimental electron scattering cross section, these densities are fundamental to much of nuclear structure physics.

The Dirac equation is used to calculate the vector charge density and tensor density, because the charge density from the analysis of the experimental data may be compared with proton charge densities obtained from various models …

Dynamics Of Dislocation-Mediated Melting In A Two-Dimensional Lattice In The Presence Of An Oscillatory Applied Strain, Arnold J. Dahm, M. A. Stan, Rolfe G. Petschek

Faculty Scholarship

The temperature and frequency dependence of the power dissipated in a two-dimensional crystal subjected to an applied strain is shown to exhibit a distinct signature for dislocation-dissociation melting. The power absorption is analogous to the case of thin helium films subjected to an applied velocity field. Power loss by dislocation motion in the compressional mode is severely limited by the presence of nonequilibrium densities of interstitial and vacancy defects that are created or annihilated by dislocation climb. Tables of analogs between dislocations, vortices, and charges in two-dimensional systems are presented. The relation of the results to published experiments is discussed.

Critical Behavior Of A Frustrated Ising System, O. Heinonen, Rolfe G. Petschek

Faculty Scholarship

Finite-size-scaling analysis of a simulation of the critical behavior of a nonrandom three-dimensional frustrated system yields a tricritical-like behavior not predicted by a simple Landau-Ginzburg-Wilson theory. We argue that, because of the frustration, the free energy of many phases is close to that of the observed ordered phase and that a complete theory must take into account interactions between fluctuations of order parameters of all these phases. We suggest that these properties are generic to frustrated systems. Related transitions in the model are also discussed.

Bethe Stopping-Power Theory For Heavy-Target Atoms, P.T. Leung

Physics Faculty Publications and Presentations

The Bethe stopping-power theory is considered in the context of heavy target atoms in which the relativistic effects of the target electrons are partially accounted for within the semirelativistic and independent-particle description. Numerical results show that, for target elements with large atomic numbers, these relativistic effects can become comparable with other corrections such as the shell correction, the Barkas effect, and the Bloch term.

Hamiltonian Formulation Of Induced Gravity In Two Dimensions, Charles G. Torre

Aerospace, Physics, and Space Science Faculty Publications

A Hamiltonian formulation of the theory of induced gravity in two dimensions is constructed. This formulation differs from previous efforts in that the formalism is covariant under all relevant transformation groups. In particular, spatial diffeomorphism covariance and/or invariance is manifest throughout; the phase space carries a representation of the Lie algebra of the spacetime diffeomorphism group; the group of conformal isometries is projectively represented on the phase space as a symmetry group. The key ingredient that allows covariance with respect to the above groups is the enlargement of the gravitational phase space by the inclusion of the cotangent bundle over …

Angular And Energy Distributions Of Electrons From 7.5- 150-Kev Proton Collisions With Oxygen And Carbon Dioxide, Wen-Qin Cheng, M. Eugene Rudd, Ying-Yuan Hsu

M. Eugene Rudd Publications

Cross sections for the ejection of electrons, differential in the angle and energy of emission, were measured for proton collisions with two molecular gases, oxygen and carbon dioxide, over the primary energy range of 7.5-150 keV and an angular range of 10° to 160°. The energy distributions, obtained by integration over the angle, were fitted by an analytical model. A discrepancy in the angular distributions compared to those of Gibson and Reid [J. Phys. E 17, 1227 (1984); J. Phys. B 19, 3265 (1986); Radiat. Res. 112, 418 (1987); Australian Atomic Energy Commission Report No. AAEC/E659, 1987 (unpublished)] is discussed. …

Navier-Stokes Analysis Of Cold Gas Scramjet Nozzle-Afterbody Flowfields, Walter C. Engelund

Mechanical & Aerospace Engineering Theses & Dissertations

The recent renewal of interest in hypersonic aerodynamics, brought about largely in part due to the development of the National Aerospace Plane (NASP), is resulting in an increased reliance on computational fluid dynamics for flowfield data in this flight regime. The design of the nozzle-afterbody section for a hypersonic transport such as the NASP is currently underway, and is being conducted using both computational fluid dynamics and cold, non-reacting, simulant gas experimental models. In this study, a computational analysis is conducted for the flow through a scramjet nozzle-afterbody test section.

Computations have been performed for a cold gas simulation of …

Domain Decomposition For Multigrid, Finite Volume Flow Solvers, Victor Robert Lessard

Mechanical & Aerospace Engineering Theses & Dissertations

Computing the flow fields about three-dimensional complex configurations accurately becomes a difficult task, if it is attempted to generate a single, body fitted grid with proper clustering. The domain decomposition methods, which divide the computational domain into less complex subdomains, are extensively used to decrease the grid generation workload. A domain decomposition technique also allows the use of different solution methods for different subdomains. The objective of this work is to develop a domain decomposition method via overlapping/embedding the component grids, which is to be used by upwind, multigrid, finite volume solution algorithms. A computer code, given the name MaGGiE, …

Application Of Shape Sensitivity Analysis For Computation Of Transient Free-Surface Flows, Frank Nicolas Michel

Mechanical & Aerospace Engineering Theses & Dissertations

Shape sensitivity analysis is introduced into a numerical scheme simulating a transient free-surface flow and applied to the case of a fluid advancing through a bed of cylinders. For this incompressible Newtonian flow, viscous forces are dominant. A penalty function finite element formulation is used to solve the problem. Coordinates of nodes on the moving boundary are chosen as design variables and an analytical formulation of the gradient of the finite element algebraic system, with respect to these variables, is derived.

In a numerical example, the results obtained with and without sensitivity analysis are compared. The efficiency and accuracy of …

Radiative Kaon Capture At Rest In Hydrogen, William J. Fickinger, D. K. Robinson

Faculty Scholarship

The photon spectrum from K- stopping in liquid hydrogen has been measured with a high-resolution (1.5% FWHM at 300 MeV) NaI(Tl) detector. The branching ratios for K-p→Λγ (Eγ=281.4 MeV) and K-p→Σ0γ (Eγ=219.5 MEV) were obtained. The results are RΛγ=(0.86±0.07-0.08+0.1)×10-3 and RΣ0γ=(1.44±0.20-0.10±0.12)×10-3 where the first error is statistical and the second systematic. These results are not in good agreement with published predictions or with previous Λγ measurements.

Hall-Effect Depletion Corrections In Ion-Implanted Samples: Si29 In Gaas, David C. Look

Physics Faculty Publications

The sheet free‐carrier concentration in a thin, conducting layer on an insulating substrate is lower than the net, sheet‐dopant concentration because of free‐carrier depletion in the surface and interface regions. Here we develop an algorithm to give the true, net sheet‐donor concentration from the measured sheet‐Hall concentration under the assumption of a Gaussian donor profile, which is usually sufficiently accurate for ion‐implanted samples. Correction curves are generated for Si²⁹ ions implanted into GaAs at energies of 60, 100, 130, 150, and 200 keV, and at doses of 1×10¹¹–2×10¹⁴ ions/cm². Also, the …

One-Dimensional Quantum Transport In The Presence Of Traps, Paul Ernest Parris

Physics Faculty Research & Creative Works

A study is made of the survival probability P(t) for a quantum particle moving coherently on an ordered one-dimensional chain containing randomly placed irreversible traps in concentration q. We consider two separate models of the trapping process, focusing on the long-time limit of each. In the first model, intended to describe substitutional traps, the trapping impurities act as disruptive absorbing barriers which prevent further motion along the chain. For this model it is shown that -ln[P(t)]1/4t^1/4. The second model is intended to describe interstitial trapping impurities which do not disrupt the transport. It is argued for this case …

Full Optical Potential For The Electron-Hydrogen Entrance Channel, Igor Bray, Don H. Madison, Ian E. Mccarthy

Physics Faculty Research & Creative Works

Differential and total elastic and total reaction cross sections are calculated for electron-hydrogen scattering at 30, 100, and 400 eV using an ab initio optical potential that treats bound and continuum nonelastic channels in the distorted-wave Born approximation. Multichannel and partial wave expansions are carried out to numerical convergence. Convergence criteria and quadratures for the continuum-energy integration are chosen for 1% overall accuracy. Results are compared with experiment and less detailed calculations.

Post-Prior Symmetrical First-Order T Matrix For Charge Transfer, Jack C. Straton, M. D. Girardeau

Physics Faculty Publications and Presentations

The Fock-Tani Hamiltonian is found for systems containing two protons and one electron. It is shown that a post-prior symmetrical T-matrix element for a⁺ + (b⁺ c^-)→(a⁺ c^-)+b⁺ may be found from that of the simpler proton-proton-electron system if a and b are treated as isospin projections of a single type of nucleon. The Coulomb-exchange contribution to the inelastic (isospin flip) scattering of this system gives a first-order T matrix that is completely symmetrical with respect to post and prior interactions and orthogonalizations, a symmetry of the exact …

The Chromosphere Of Beta Cassiopeiae, Terry J. Teays, Edward G. Schmidt, Massimo Fracassini, Laura E. Pasinetti Fracassini

Edward Schmidt Publications

We have carried out high-resolution, long-wavelength IUE observations and ground-based photometry of the δ Scuti star β Cas. The ground-based observations were used together with previous results of Antonello et al. to ensure that the IUE observations were correctly phased relative to the photometric variation. Fluxes for the emission core of the Mg _II k λ2796 line were obtained from the ultraviolet spectra over several cycles in 1986 and 1987. We found that there is an increase in the emission during part of the cycle but it occurs near minimum light in contrast to another δ Scuti star, ρ Pup, …

The Response Of The Alanine Detector After Charged-Particle And Neutron Irradiations, M. P. R. Waligorski, G. Danialy, Robert Katz

Robert Katz Publications

Radiosensitivity parameters of track structure theory, representing alanine as a one-hit detector, have been fitted for this free-radical amino-acid system on the basis of the available experimental data on the relative effectiveness of alanine after charged particle and neutron irradiations. The experimental data set can be reproduced by theoretical calculations, roughly to within experimental accuracy. A charged-particle “equivalent radiation” is introduced which can mimic the response of alanine to neutron irradiations. Implications of the results of model calculations for alanine on the shape of the radial distribution of δ-ray dose postulated by track theory, are discussed.

Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel

Physics Faculty Research & Creative Works

We have observed dielectronic and direct excitation of H-like S¹⁵⁺ and Ca¹⁹⁺ and He-like Ti²⁰⁺ ions in silicon channels caused by collision with weakly bound target electrons which behave as a free-electron gas. As in vacuo, relaxation of the doubly excited states can occur radiatively leading to ions of decreased charge, but in a crystal channel collisional effects can cause double ionization. The effects are seen in both the x-ray yields and charge-state fractions, and, in the case of Ti²⁰⁺, in charge-state x-ray coincidences.

Evaluation Of Equilibrium Turbulence For A Hypersonic Boundary Layer At Nonadiabatic Wall Conditions, Cindy W. Albertson

Mechanical & Aerospace Engineering Theses & Dissertations

This paper presents an experimental study to characterize the compressible turbulent boundary layer produced along a flat plate in the NASA Langley 8-Foot High Temperature Tunnel and determine the test conditions necessary to achieve equilibrium turbulence. In addition, the present study extends the data base for equilibrium compressible turbulent boundary layers over quasi-isothermal walls which are far from the adiabatic wall temperature. The measurements consist of pilot pressure, static pressure, and total temperature distributions in the boundary layer. A flat plate measuring 9.7 feet long and 4.3, feet wide was used for the study to provide a naturally turbulent boundary …

Nuclear Fragmentation Energy And Momentum Transfer Distributions In Relativistic Heavy-Ion Collisions, Ferdous Khan

Physics Theses & Dissertations

An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.

An Improved Correction Algorithm For Number Density Measurements Made With The Forward-Scattering Spectrometer Probe, James A. Lock, Edward A. Hovenac

Physics Faculty Publications

A correction factor to the number density measured by the Forward Scattering Spectrometer Probe (FSSP) which compensates for dead time and coincidence errors was determined by calculating the probabilities of and the average number of particles in the six possible types of dead time and coincidence events. These probabilities and averages were calculated by means of a probabilistic model based on Poisson statistics. A Monte Carlo computer simulation of the FSSP operation was also carried out and the number density correction factor was compared with the Monte Carlo data. For an actual number density of 2000/cm³, it was …

A Correction Algorithm For Particle-Size Distribution Measurements Made With The Forward-Scattering Spectrometer Probe, James A. Lock, Edward A. Hovenac

Physics Faculty Publications

Multiparticle coincidence events in the scattering volume of the forward-scattering spectrometer probe (FSSP) cause the instrument to bias the measurement of the particle size distribution of atmospheric aerosols toward large diameters. We employ a probabilistic model based on Poisson statistics to determine the average diameter and rms width of the actual size distribution as functions of the average diameter and rms width of the measured distribution. We compare our predictions to a Monte Carlo simulation of the FSSP operation

Transitions And Modulated Phases In Chiral Tilted Smectic Liquid Crystals, George A. Hinshaw Jr., Rolfe G. Petschek

Faculty Scholarship

Modulated phases that occur in tilted chiral smectic liquid crystals are discussed within mean-field theory in thin films and in bulk. A chiral term in the free energy containing three order parameters and one gradient can make the free energy of certain defects negative or the bend elastic constant negative. Assuming various possible behaviors for these defect energies we find either a striped state with parallel defect walls or a lattice of hexagonal unit cells containing disclinations bounded by intersecting defect walls in films. Rather different transitions to the striped phase occur when this elastic constant is either positive or …

Orientation Of Hydrogen 2P After Tilted-Foil Excitation, C. J. Liu, Timothy J. Gay, K. P. Schuler

Timothy J. Gay Publications

The circular polarization of Lyman-α photons resulting from beam-tilted-foil excited H(2p) was measured at energies between 9 and 20 keV with foil tilt angles up to 60°. Various interaction models are used to fit the data, and their physical significance is discussed.

Long-Range Hopping In Substitutionally Disordered Solids, Paul Ernest Parris

Physics Faculty Research & Creative Works

A theoretical approach for studying charge-carrier and energy diffusion due to long-range hopping in substitutionally disordered solids is presented. Unlike some earlier theories, which invoke a pair approximation to treat back-transfer processes, the current theory makes use of the exact solution to an appropriate single-defect problemone in which long-range jumps into, out of, and between both the defect site and all other active sites in the lattice are explicitly included. From this exact solution a new long-range effective-medium theory is constructed to describe the configurationally averaged transport properties of the disordered system.

Spectroscopy Of The 6p3/2Np States Of Barium, J. Greg Story, E. G. Yap, William E. Cooke

Physics Faculty Research & Creative Works

The 6p_3/2np states of barium have been observed for n values between 14 and 21. The energies, linewidths, and transition strengths have been measured and characterized in terms of one- and two-electron interactions, using a single-configuration approximation.

The Decomposition Of [Mn(Co)5]2(Μ-Sih2), G.T. Stauf, Peter A. Dowben, K. Emrich, W. Hirschwald, N.M. Boag

Peter Dowben Publications

The prospect of using chemical vapor deposition to deposit mixed metals and silicides from a single source compound is attractive but largely uninvestigated. Studies of decomposition energies of such compounds are nearly nonexistent. One such compound which has successfully been used to make a silicide coating is [Mn(CO)₅ 1₂ (μ-SiH₂). We have used electron impact mass spectroscopy, photoionization mass spectroscopy, and photoabsorption to determine bond energies within this compound. The combination of methods allows a high degree of confidence in the resultant ionization and fragment appearance potentials. Some possible mechanisms of decomposition are discussed. A complete …

Decay Of Molecules At Corrugated Thin Metal Films, P.T. Leung, Young Sik Kim, Thomas F. George

Physics Faculty Publications and Presentations

The problem of the decay rate for molecules at corrugated thin metal films is considered theoretically via a classical phenomenological approach by generalization of a previous theory for a single rough surface. In particular, numerical results are worked out in detail for grating films with various possible arrangements of the two grating surfaces, and for both cases with a supported and a free-standing film. Effects due to cross coupling into the long- and short-range surface plasmons are observed, and correlations to recent experiments performed by Gruhlke, Holland, and Hall are made. It is suggested that fluorescence experiments with pulsed-laser excitations …