Physics Commons^™

First-Principles Study Of Phase Stability In Cu-Zn Substitutional Alloys, P. E. A. Turchi, M. Sluiter, F. J. Pinski, Duane D. Johnson, D. M. Nicholson, G. M. Stocks, J. B. Staunton

Duane D. Johnson

A parameter-free approach to phase stability in Cu-Zn substitutional alloys is shown to describe order-disorder phenomena and structural transformations with remarkable accuracy. The method is based on a multiple-scattering description of the electronic structure properties of the random alloy. Configurational order is treated within the generalized perturbation method and the concentration-functional theory. Thermodynamical properties of α and β brasses are derived from the cluster variation method. This advanced scheme is of general validity and is expected to yield similarly accurate results for other Hume-Rothery alloys.

An Experimental Investigation Of The Finite Time Efficiency Of A Peltier Refrigeration Device, Thomas Schneider

Dissertations and Theses

Since the need of energy conservation has become more and more urgent in the past decades, there has been an increased interest in the study and development of more efficient energy conversion systems. One of the fields that have arisen from that endeavor is a branch of physics called Finite Time Thermodynamics (FIT). It may be said that FIT was initiated through the famous paper by Curzon and Ahlborn (1975) that established new bounds on the efficiency of a finite time Carnot heat engine. Before, the traditional treatments gave a fundamental upper limit on the efficiency of any heat engine. …

Inhibited Spontaneous Emission By Photonic Band Gaps In A Square Lattice Of Periodic Dielectric Medium, Abdullah Al-Ghamdi

Masters Theses

The concepts of band theory for electrons can be employed to describe the behavior of electromagnetic waves propagating in two-dimensional, periodic dielectric structures. These two-dimensional, periodic structures can produce photonic band gaps in which the spontaneous emission by atoms embedded in the structure is prohibited and as a result the performance of many semiconductor devices can be enhanced. The calculations are based on finding the eigenvalues of the algebraic equation for the frequencies of electromagnetic waves moving in a square lattice composed of square dielectric rods with different dielectric constants.

33rd Rocky Mountain Conference On Applied Spectroscopy

Rocky Mountain Conference on Magnetic Resonance

Program and registration information for the 33rd annual meeting of the Rocky Mountain Conference on Applied Spectroscopy, sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 28 - August 1, 1991.

On Shock Capturing For Liquid And Gas Media, Tze Jang Chen

Mathematics & Statistics Theses & Dissertations

The numerical investigation of shock phenomena in gas or liquid media where a specifying relation for internal energy is absent poses special problems. Classically, for gas dynamics the usual procedure is to employ a splitting scheme to remove the source terms from the Euler equations, then up-wind biased shock capturing algorithms are built around the Riemann problem for the system which remains. However, in the case where the Euler equations are formulated in the term of total enthalpy, a technical difficulty associated with equation splitting forces a pressure time derivative to be treated as a source term. This makes it …

Investigation Of Real-Time Optical Scanning Holography, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

Real-time holographic recording using an optical heterodyne scanning technique was proposed by Poon in 1985. The first part of this dissertation provides a detailed theoretical treatment of the technique, based on a Gaussian beam analysis. Topics to be addressed include the derivations of the optical transfer function (OTF) and impulse response of the scanning holographic recording system, reconstructed image resolution and magnification, methods of carrier frequency hologram generation and experimental verification of the recording technique based on careful measurements of a hologram corresponding to a simple transmissive slit. Furthermore, computer simulations are presented pertaining to the incoherent nature of the …

Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu

Chemical and Materials Engineering Faculty Publications

In industry there are many examples of absorption of a gas with or without chemical reaction in the liquid phase. In physical absorption, a particular gaseous component is removed from a gas mixture due to its larger solubility in the liquid phase solvent. The removal of butane and pentane from a refinery gas mixture by a heavy oil in the liquid phase is an example of physical absorption. In absorption with chemical reaction, the gaseous component to be removed transfers across the gas-liquid interface due to a difference in the bulk chemical potentials or concentrations in the two phases. The …

Fourier Transform Infrared (Ftir) Spectroscopy Analysis Of Combustion Aerosol, Gary Jacquin

Opportunities for Undergraduate Research Experience Program (OURE)

In conjunction with my co-op program at McDonnell-Douglas, my current OURE project is the analysis of combustion aerosols using Fourier Transform Infrared (FTIR) Spectroscopy. Aerosol science is a very important field as it is concerned with atmospheric chemistry, atmospheric physics, climate, public health, and environmental issues.

In the Cloud and Aerosol Sciences Laboratory (CASL) at UMR, combustion aerosols are generated by an in-house designed torch or burner. The fuels, JP4 and JP5, are provided by McDonnell-Douglas. Some other commercial fuels are also used. The primary objective of my OURE project was to generate and collect combustion aerosols for chemical analysis. …

Transport Processes And Traveling Waves In Systems With Local Nonequilibrium, Sergey Sobolev

Sergey Sobolev

No abstract provided.

Origins Of Compositional Order In Nipt Alloys, F. J. Pinski, B. Ginatempo, Duane D. Johnson, J. B. Staunton, G. M. Stocks, B. L. Gyorffy

Duane D. Johnson

We investigate the cause of compositional ordering in fcc Ni0.50Pt0.50 on the basis of a first-principles theory of electronic structure and finite-temperature concentration fluctuations. We treat the size effect, electronegativity, and band filling on an equal footing and find that the first of these dominates, leading to L10 ordering in agreement with experiment. An electronic origin is given for the metallurgical ‘‘rule of thumb’’ that alloys comprised of big atoms and little atoms tend to order into simple stuctures.

The Interaction Between Dislocations And Intergranular Cracks, H. Zhang, Alexander H. King, R. Thomson

Alexander H. King

The elastic interactions of dislocations and intergranular cracks in isotropic materials have been studied. In the first part of the paper, a model based on the Rice–Thomson theory is established under which the conditions for dislocation emission and crack propagation can be described in terms of an emission surface, cleavage surface, and loading line in the local k-space associated with a mixed mode intergranular crack. For a given crack, the local k-field changes with the emission of dislocations from the crack tip, which alters the balance of cleavage and emission. In the second part, we present experimental results of in …

The Slater–Pauling Curve: First Principles Calculations Of The Moments Of Fe1 − C Ni C And V1 − C Fe C, Duane Johnson, F. Pinski, J. Staunton

Duane D. Johnson

We have performed calculations of the electronic structure of the random substitutional alloys Fe1−c Ni c and V1−c Fe c using the spin‐polarized, self‐consistent Korringa–Kohn–Rostoker coherent‐potential approximation (KKR‐CPA) method. This is a first principles method based on spin density functionaltheory and a local spin density approximation for the exchange and correlation functional. For fcc Fe1−c Ni c , a range of volumes were considered for 0.25

Magnetic Field Strength Of Toroidal Plasma Equilibria, David Alan Garren

Dissertations, Theses, and Masters Projects

The goal of nuclear fusion research is to confine a deuterium-tritium plasma at a sufficiently high temperature (15 keV) and density (3 $\times$ 10$\sp{20}$ m$\sp{-3}$) for a sufficient length of time (1 sec) to produce net fusion power. One means to attain the required plasma confinement is to embed the plasma within a magnetic field. The global structure of this magnetic field determines the variation of magnetic field strength within the surfaces of constant plasma pressure. This field strength variation in turn determines many of the stability and confinement properties of the plasma. This dissertation gives the first detailed exposition …

Electrical Conductivity, Seebeck Coefficient And Defect Chemistry Of Ca-Doped Ycro3, G. F. Carini, Harlan U. Anderson, Don M. Sparlin, M. M. Nasrallah

Materials Science and Engineering Faculty Research & Creative Works

The electrical transport behavior and defect structure of Ca-doped YCrO₃ were studied using electrical conductivity and Seebeck coefficient measurements as a function of oxygen activity and temperature. Defect models derived from the electrical conductivity data were found to adequately relate the concentration of charge carriers to the acceptor dopant and oxygen vacancy concentrations. Thermodynamic properties were calculated and found to be consistent with the model. Activation energy and carrier mobility data were also obtained. The analysis of the electrical conductivity, Seebeck and mobility data suggest that the conduction process in Ca-doped YCrO₃ occurs via the small polaron hopping …

Defect Structure, Nonstoichiometry, And Phase Stability Of Ca-Doped Ycro3, G. F. Carini, Harlan U. Anderson, M. M. Nasrallah, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

The dependence of the defect structure of Ca-doped YCrO₃ on oxygen activity and temperature was investigated by high temperature thermogravimetric measurements. Defect models developed from electrical conductivity data obtained in a previous study were used to interpret the thermogravimetric data. A correlation was found between the electrical conductivity and the thermogravimetric data which suggested that these data were concomitantly dependent on the acceptor dopant and oxygen vacancy dependance of the thermodynamic parameters. Kröger-Vink type diagrams showing the regions of stability with respect to oxygen activity and temperature were constructed. The TGA data show that Ca-doped YCrO₃ is even …

Nuclear Magnetic Resonance Studies Of Amorphous Nickel-Zirconium Hydrides, Harris Clarence Hoke Jr.

Dissertations, Theses, and Masters Projects

This research deals with one aspect of the scientific field of hydrogen in metals. The study of hydrogen in metals is technologically important for many reasons, among them is the use of hydrogen in metals to store energy. Hydrogen related energy technology is particularly attractive because hydrogen can be extracted from water, our most abundant resource, and can be used without any pollution. Metal hydrides may one day be widely used for automotive propulsion in cars, in batteries, and many other energy conversion devices. Amorphous NiZr is particularly interesting for hydrogen storage because high concentrations of hydrogen can be sorbed …

Effects Of Sample Orientation On The Corrosion Of Zinc In Ammonium Sulfate And Sodium Hydroxide Solutions, D. Abayarathna, Edward Boyd Hale, Thomas J. O'Keefe, Y. M. Wang, D. Radovic

Physics Faculty Research & Creative Works

The corrosion and electrochemical properties of three zinc single crystal surfaces with different orientations have been investigated. In near-neutral 1 M (NH₄)₂SO₄, the corrosion rates on all three surfaces were found to be similar. However, the SEM morphologies of the corresponding corroded surfaces were markedly different from each other, but consistent with preferential attack of {1120} surfaces. In alkaline 0.5 N NaOH solution, the three sample orientations showed significantly different reactivities, with the (1120) surface exhibiting the highest reactivity and corrosion rate. Here, passivation ultimately occurred and the difference in the corrosion performance of …

Electric Field Induced Emission As A Diagnostic Tool For Measurement Of Local Electric Field Strengths, A. N. Dharamsi, K. H. Schoenbach

Bioelectrics Publications

The phenomenon of electric field induced (EFI) emission is examined in several diatomic and polyatomic molecules. The possibility of using this phenomenon as a diagnostic tool to measure, nonintrusively, the strength and direction of local electric fields in plasmas is discussed. An estimate of the EFI signal emitted in a typical application plasma is given. This yields a lower bound on the detector sensitivity necessary to exploit EFI emission in practical applications. It is concluded that, at present, the EFI signal could be measured by some very sensitive infrared detection schemes available. Current progress in infrared detector technology, if maintained, …