Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. …

Large-scale numerical computations associated with rock mechanics problems have required efficient and economical models for predicting temperature, stress, failure, and deformed structural configuration under various loading conditions. To meet this requirement, the complex dependence of the properties of geological materials on the time and temperature is modified to yield a reduced time scale as a function of time and temperature under the thermorheologically simple material (TSM) postulate. The thermorheologically linear concept is adopted in the finite element formulation by uncoupling thermal and mechanical responses. The thermal responses, based on transient heat conduction or convective-diffusion, are formulated by using the two-point recurrence scheme and the upwinding scheme, respectively. An incremental solution procedure with the implicit time stepping scheme is proposed for the solution of the thermoviscoelastic response. The proposed thermoviscoelastic solution algorithm is based on the uniaxial creep experimental data and the corresponding temperature shift functions, and is intended to minimize computational efforts by allowing large time step size with stable solutions. A thermoelastic fracture formulation is also presented by introducing the degenerate quadratic isoparametric singular element for the thermally-induced line crack problems. The stress intensity factors are computed by use of the displacement method. Efficiency of the presented formulation and …

Liquid fossil fuels, both petroleum and synthetically derived oils, are exceedingly complex mixtures of thousands of components. The effect of many of these energy-related components on the environment is largely unknown. Octanol/water distribution coefficients relate both to toxicity and to the bioaccumulation potential of chemical components. Use of these partition data in conjunction with component concentrations in the oils in environmental models provides important information on the fate of fossil fuel components when released to the environment. Octanol/water distribution data are not available for many energy-related organic compounds, and those data that are available have been determined for individual components in simple, one-component octanol/water equilibrium mixtures. In this study, methods for determining many octanol/water distribution coefficients from aqueous extracts of oil products were developed. Sample aqueous mixtures were made by equilibrating liquid fossil fuels with distilled water. This approach has the advantage of detecting interactions between components of interest and other sample components. Compound types studied included phenols, nitrogen bases, hydrocarbons, sulfur heterocyclic compounds, and carboxylic acids. Octanol/water distribution coefficients that were determined in this study ranged from 9.12 for aniline to 67,600 for 1,2-dimethylnaphthalene. Within a compound type, distribution coefficients increased logarithmically with increasing alkyl substitution and molecular weight. …

The Heavy Ion Fusion group at Lawrence Berkeley Laboratory has constructed the One Ampere Cesium Injector as a proof of principle source to supply an induction linac with a high charge density and high brightness ion beam. This is studied here. An electron beam probe was developed as the major diagnostic tool for characterizing ion beam space charge. Electron beam probe data inversion is accomplished with the EBEAM code and a parametrically adjusted model radial charge distribution. The longitudinal charge distribution was not derived, although it is possible to do so. The radial charge distribution that is derived reveals an unexpected halo of trapped electrons surrounding the ion beam. A charge fluid theory of the effect of finite electron temperature on the focusing of neutralized ion beams (Nucl. Fus. 21, 529 (1981)) is applied to the problem of the Cesium beam final focus at the end of the injector. It is shown that the theory's predictions and assumptions are consistent with the experimental data, and that it accounts for the observed ion beam radius of approx. 5 cm, and the electron halo, including the determination of an electron Debye length of approx. 10 cm.

The development of morphology of electrodeposited zinc was investigated by studying the initial stages of deposition. Zinc was deposited galvanostatically from 1.0 M ZnCl/sub 2/ electrolyte (0.7 < pH < 4.6) on rotating disc electrodes at current densities from 5 to 130 ma/cm/sup 2/. Pine glassy carbon, Union Carbide pyrolytic graphite, Gould pyrolytic graphite, Exxon graphite loaded polymer, and platinum substrates were used. The number densities of nodules (diameter greater than 1 ..mu..m), typically encountered during incipient morphological development, were measured using scanning electron microscopy and image analysis. Nodule densities up to 7 x 10/sup 4/ nodules/mm/sup 2/ were measured.