12 Matching Results

Search Results

Results: 1 - 12
open access

CARBON AND DEUTERIUM NUCLEAR MAGNETIC RESONANCE IN SOLIDS

Description: In Chapter I we present the results on a study of cross polarization dynamics, between protons and carbon-13 in adamantane, by the direct observation of the dilute, carbon-13, spins. These dynamics are an important consideration in the efficiency of proton enhancement double-resonance techniques and they also provide good experimental models for statistical theories of cross relaxation. In order to test these theories we present a comparison of the experimental and theoretical proton dipolar fl… more
Date: July 1, 1976
Creator: Shattuck, Thomas Wayne
Partner: UNT Libraries Government Documents Department
open access

Studies of design parameters in the fabrication of Nb--Al--Ge superconductors by the powder metallurgy infiltration method

Description: Experimental studies have been carried out in which the A15 phase of the Nb-Al-Ge system has been synthesized in the form of thin filaments contained in form rolled wires. A powder metallurgy approach has been used to achieve controlled porosity in compacts of sintered niobium powder. Infiltration with an aluminum-germanium eutectic alloy followed by mechanical deformation has produced small interconnected filaments embedded in the Nb matrix. Diffusion heat treatment for a short time transforms… more
Date: December 1, 1976
Creator: Granda, Jose J.
Partner: UNT Libraries Government Documents Department
open access

Separated-pair independent particle model and the generalized Brillouin theorem: ab initio calculations on the dissociation of polyatomic molecules

Description: A method is developed to optimize the separated-pair independent particle (SPIP) wave function; it is a special case of the separated-pair theory obtained by using two-term natural expansions of the geminals. The orbitals are optimized by a theory based on the generalized Brillouin theorem and iterative configuration interaction (CI) calculations in the space of the SPIP function and its single excitations. The geminal expansion coefficients are optimized by serial 2 x 2 CI calculations. Formul… more
Date: January 1, 1976
Creator: Sundberg, K. R.
Partner: UNT Libraries Government Documents Department
open access

Interrelationships between thermal history and mechanical properties of a secondary hardening steel. [Vasco MA steel]

Description: Commercial secondary hardening steel, VASCO MA, has been subjected to modified heat treatments to introduce mixed microstructures of martensite and lower bainite. Dilatometry, tensile testing, hardness measurements and slow-bend testing have been carried out and the mechanical properties obtained have been correlated to microstructure using scanning electron microscopy and metallography. Duplex microstructures containing small amounts of lower bainite are found to show an increased toughness (a… more
Date: December 1, 1976
Creator: Kar, N. J.
Partner: UNT Libraries Government Documents Department
open access

Self-diffusion of Co$sup 60$ in crystals of Co$nu$sub 1-x/O

Description: Tracer self-diffusion coefficients were measured as functions of temperature and deviations from stoichiometry. The arc-transfer technique of crystal growth was found to produce crystal of Co/sub 1-x/O of essentially the same purity as the starting Co rod, and the quality was comparable to commercially available crystals grown by Verneuil process. Measurements at x = 0.005 in Co/sub 1-x/O showed the Co tracer self-diffusion coefficient to be D = 3.88 x 10$sup -4$ exp (--31600 +- 2400/RT) cm$sup… more
Date: January 1, 1976
Creator: Rahman, S. F.
Partner: UNT Libraries Government Documents Department
open access

Electromagnetic form factors of hadrons

Description: A vector meson dominance model of the electromagnetic form factors of hadrons is developed which is based on the use of unstable particle propagators. Least-square fits are made to the proton, neutron, pion and kaon form factor data in both the space and time-like regions. A good fit to the low-energy nucleon form factor data is obtained using only rho, $omega$, and phi dominance, and leads to a determination of the vector meson resonance parameters in good agreement with experiment. The nucleo… more
Date: January 1, 1976
Creator: Zidell, V. S.
Partner: UNT Libraries Government Documents Department
open access

Use of variational techniques for the estimation of neutron detection efficiency

Description: The neutron detection efficiency is a parameter required in the measurement of reactivity by the modified source technique. The direct solution of the detection efficiency at a perturbed state is costly. To solve for this, a particular variational functional, the Lewins' type variational functional, is presented. The functional is a ratio of two other functionals, each dealing with a reaction rate. The evaluation of this particular functional was done by treating the numerator and the denominat… more
Date: February 1, 1976
Creator: Lin, S.; Robinson, J.C. & Flanagan, G.F.
Partner: UNT Libraries Government Documents Department
open access

Iterative solution of the diffusion and P$sub 1$ finite element equations

Description: A method for obtaining solutions to the time-independent Boltzmann neutron transport equation on triangular grids with nonorthogonal boundaries and anisotropic scattering is developed. A functional is obtained from the canonical form of the multigroup transport equation. The angular variable is then removed by expanding the functional in spherical harmonics, retaining only the first two moments and limiting the anisotropic scattering to be linear. The finite element method is then implemented b… more
Date: February 1, 1976
Creator: Tomlinson, E.T.; Robinson, J.C. & Vondy, D.R.
Partner: UNT Libraries Government Documents Department
open access

High temperature vaporization and thermodynamic study of the scandium-- sulfur system

Description: Results of studies on the stoichiometry, structure, vaporization behavior, and thermodynamic properties of the Sc--S system are reported. The thermodynamic results for the stability of ScS(s) are compared with reported results for other transition-metal and rare-earth monosulfides. Various models are discussed in regard to their ability to describe the bonding in these refractory solids. (JRD)
Date: January 1, 1976
Creator: Tuenge, R. T.
Partner: UNT Libraries Government Documents Department
open access

Proton--proton interactions at 200 and 300 GeV/c

Description: The reactions pp $Yields$ pp $pi$$sup +$pi$sup -$ and pp $Yields$ pp$pi$$sup +$$pi$$sup -$$pi$$sup +$$pi$$sup -$ at 200 and 300 GeV/c were investigated using the Fermilab 30-inch hydrogen bubble chamber and downstream wide-gap spark chambers. This analysis is based upon approximately 9500 4- pronged and 6-pronged events. The cross sections were consistent with pomeron dominance for these reactions. The final state pp $pi$$sup +$$pi$$sup -$ is dominated by single diffractive dissociation, whose … more
Date: January 1, 1976
Creator: Ogino, F.
Partner: UNT Libraries Government Documents Department
open access

Gamma-ray decay schemes for $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr

Description: A study of the gamma-ray de-excitation following the beta decays of $sup 93$Kr, $sup 93$Rb, and $sup 93$Sr using the TRISTAN on-line separator facility is reported. Gamma-ray singles and gamma-gamma coincidence measurements were made using Ge(Li) detectors. Of the 162 gamma rays observed in the decay of $sup 93$Sr, 143, representing more than 99 percent of the total gamma-ray intensity observed, were placed in a level scheme containing 36 levels. For the decay of $sup 93$Rb, 243 gamma rays were… more
Date: January 1, 1976
Creator: Bischof, C.J.
Partner: UNT Libraries Government Documents Department
open access

A study of the interaction of x-rays and acoustic, stress and shock waves in solids

Description: The primary emphasis of this thesis involves an investigation of techniques for the control and modulation of x-ray radiation through acoustic perturbation of solids. The use of x-ray diffraction and x-ray optical techniques for the study of acoustic fields and atomic motion was also investigated. Analysis of the basic properties of x-ray propagation in solids reveals that practical methods for x-ray control or modulation must involve changes in the spatial configuration of x-ray scatterers. Nu… more
Date: November 1, 1976
Creator: Hauer, A.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen