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A transient, quadratic nodal method for triangular-Z geometry

Description: Many systematically-derived nodal methods have been developed for Cartesian geometry due to the extensive interest in Light Water Reactors. These methods typically model the transverse-integrated flux as either an analytic or low order polynomial function of position within the node. Recently, quadratic nodal methods have been developed for R-Z and hexagonal geometry. A static and transient quadratic nodal method is developed for triangular-Z geometry. This development is particularly challengi… more
Date: June 1, 1993
Creator: DeLorey, T. F.
Partner: UNT Libraries Government Documents Department
open access

X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

Description: X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some s… more
Date: June 1, 1993
Creator: Tan, G. O.
Partner: UNT Libraries Government Documents Department
open access

Differential utilization of allochthonous and autochthonous carbon by aquatic insects of two shrub-steppe desert spring-streams: A stable carbon isotope analysis and critique of the method

Description: The purpose of this study is to assess whether the carbon supporting stream food webs comes principally from terrestrial sources or is produced within the stream. Lacking data to resolve the allochthonous/autochthonous issue with any finality, stream ecologists have alternately postulated that stream carbon was principally autochthonous or principally allochthonous. Others argued that autochthonous and allochthonous carbon resources cannot be separated and that the allochthonous/autochthonous d… more
Date: June 1, 1993
Creator: Mize, A. L.
Partner: UNT Libraries Government Documents Department
open access

Toward resolving model-measurement discrepancies of radon entry into houses

Description: Analysis of the literature indicated that radon transport models significantly and consistently underpredict the advective entry into houses of soil-gas borne radon. Advective entry is the dominant mechanism resulting in high concentrations of radon indoors. My dissertation research investigated the source of the model-measurement discrepancy via carefully controlled field experiments conducted at an experimental basement located in natural soil in Ben Lomond, California. Early experiments at t… more
Date: June 1, 1993
Creator: Garbesi, K.
Partner: UNT Libraries Government Documents Department
open access

Laser-ultrasound characterization of spherical objects. G.L. report No. 5097

Description: Ceramic bearing balls are desired for high-temperature, nonlubricated use, but because of brittleness, it is important to inspect them for small (1--10 {mu}m) surface defects. Resonance spectrum of a sphere can provide information about its material properties (shear, longitudinal wave velocities); surface wave resonant modes at high frequencies provide information about surface crack density. As surface waves encounter a defect, the resonant energy will be attenuated. By comparing the surface … more
Date: June 1, 1993
Creator: Chung-kao, P. H.
Partner: UNT Libraries Government Documents Department
open access

Investigation of the relative abundance of heavy versus light nuclei in primary cosmic rays using underground muon bundles

Description: We study multiple muon events (muon bundles) recorded underground at a depth of 2090 mwe. To penetrate to this depth, the muons must have energies above 0.8 TeV at the Earth`s surface; the primary cosmic ray nuclei which give rise to the observed muon bundles have energies at incidence upon the upper atmosphere of 10 to 10{sup 5}TeV. The events are detected using the Soudan 2 experiment`s fine grained tracking calorimeter which is surrounded by a 14 m {times}10 m {times} 31 m proportional tube … more
Date: June 8, 1993
Creator: Sundaralingam, N.
Partner: UNT Libraries Government Documents Department
open access

Advances and applications of dynamic-angle spinning nuclear magnetic resonance

Description: This dissertation describes nuclear magnetic resonance experiments and theory which have been developed to study quadrupolar nuclei (those nuclei with spin greater than one-half) in the solid state. Primarily, the technique of dynamic-angle spinning (DAS) is extensively reviewed and expanded upon in this thesis. Specifically, the improvement in both the resolution (two-dimensional pure-absorptive phase methods and DAS angle choice) and sensitivity (pulse-sequence development), along with effect… more
Date: June 1, 1993
Creator: Baltisberger, J. H.
Partner: UNT Libraries Government Documents Department
open access

Quantum harmonic Brownian motion in a general environment: A modified phase-space approach

Description: After extensive investigations over three decades, the linear-coupling model and its equivalents have become the standard microscopic models for quantum harmonic Brownian motion, in which a harmonically bound Brownian particle is coupled to a quantum dissipative heat bath of general type modeled by infinitely many harmonic oscillators. The dynamics of these models have been studied by many authors using the quantum Langevin equation, the path-integral approach, quasi-probability distribution fu… more
Date: June 23, 1993
Creator: Yeh, L.
Partner: UNT Libraries Government Documents Department
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