An improved dual-frequency technique for the remote sensing of ocean currents and wave spectra

A two frequency microwave radar technique for the remote sensing of directional ocean wave spectra and surface currents is investigated. This technique is conceptually attractive because its operational physical principle involves a spatial electromagnetic scattering resonance with a single, but selectable, long gravity wave. Multiplexing of signals having different spacing of the two transmitted frequencies allows measurements of the entire long wave ocean spectrum to be carried out. A new scatterometer is developed and experimentally tested which is capable of making measurements having much larger signal/background values than previously possible. This instrument couples the resonance technique with coherent, frequency agility radar capabilities. This scatterometer is presently configured for supporting a program of surface current measurements

A Transfer Matrix Approach to Studying the Entanglement Complexity of Self-Avoiding Polygons in Lattice Tubes

Self-avoiding polygons (SAPs) are a well-established useful model of ring polymers and they have also proved useful for addressing DNA topology questions. Motivated by exploring the effects of confinement on DNA topology, in this thesis, SAPs are confined to a tubular sublattice of the simple cubic lattice. Transfer matrix methods are applied to examine the entanglement complexity of SAPs in lattice tubes. Transfer matrices are generated for small tube sizes, and exact enumeration of knotting distributions are obtained for small SAP sizes. Also, a novel sampling procedure that utilizes the generated transfer matrices is implemented to obtain independent uniformly distributed random samples of large SAPs in tubes. Using these randomly generated polygons, asymptotic growth rates for the number of fixed knot-type SAPs are estimated, and evidence is provided to support a conjectured asymptotic form for the growth of the number of fixed knot-type polygons of a given size. In particular, the evidence supports that the entropic critical exponent goes up by one with each knot factor. Additionally, a system consisting of two SAPs (called a 2SAP) in a tube is also studied to explore linking. New transfer matrices are generated for 2SAPs in small tube sizes, and exact enumeration of linking distributions are obtained for small 2SAP sizes. A sampling procedure similar to that developed for SAPs is implemented by using the 2SAP transfer matrices to obtain independent uniform samples of large 2SAPs in tubes. An asymptotic form for the number of fixed link-type 2SAPs is conjectured with some supporting evidence from the sampled 2SAPs. All the evidence obtained supports the conclusion that the knotted parts in long polymers confined to tubular environments occur in a relatively localized manner. This is supported by the entropic critical exponent results, and by preliminary evidence that average spans of knot factor patterns are not growing significantly with polygon size. Similar evidence is obtained for the knotted parts in 2SAPs. The SAP study has also revealed further characteristics of knotting in tubes. For example, when the cross-sectional area of tubes are equal, evidence indicates that knotting is more likely in more symmetrical tubes as opposed to flatter tubes. Additionally, two types of knot pattern modes have been observed and strong evidence is provided that the so-called non-local mode is dominant for small tube sizes. These two modes have also been observed in non-equilibrium simulations and in DNA nanopore experiments. The evidence for the characteristics of the linked part of 2SAPs in a tube is less conclusive but its study has opened up numerous interesting questions for further study. In summary, the novelty of the contributions in the thesis include both computational and polymer modelling contributions. Computationally: transfer matrices, Monte Carlo methods, and a novel approach for knot identification for knots in tubes are developed and extended to larger tube sizes than ever before. Polymer modelling: strong numerical evidence supporting knot localization for polymers in tubes and the first evidence regarding characterising linking for polymers in tubes are obtained

Reducibility of Aswan Ore and Sinters with Varying Basicity Ratios

THE RESULTS of the study of the reduction kinetics of sinters of different basicity ratios (0.2-2.0) as well as of Aswan ore of definite grain size (6-10) mm. by H2 gas at a definite "Redox" potential (100 1./g. 02 /hr.) at 950°C have shown that the general shape of the reduction functions of time are unique— partly parabolic and partly topochemical in nature—and that they obey the general Jeschar equation for the overall reduction process. A specific case of the general equation has been checked among other 6 formulas by modem computing techniques using an IBM electronic computer type 1620 and found to be in good agreement with the experimental results. The equation could be derived on a theoretictd basis and considers a reduction mechanism that is controlled mainly by both diffusion and chemical reaction processes as being the slowest pertaining and hence the rate determining factors in the complex reduction mechanism. Aswan ore is far more reducible than any of the other different kinds of studied fluxed or nonfluxed sinters. Also fluxed sinters made from Aswan ore by adding incre-asing amounts of lime are far more reducible by gases at a temperature level of 950°C—normally prevailing in the shaft cf a blast furnace than nonfluxed sinters

Unconventional Hall effect in oriented Ca3_3Co4_4O9_9 thin films

Transport properties of the good thermoelectric misfit oxide Ca$_3$Co$_4$O$_9$ are examined. In-plane resistivity and Hall resistance measurements were made on epitaxial thin films which were grown on {\it c}-cut sapphire substrates using the pulsed laser deposition technique. Interpretation of the in-plane transport experiments relates the substrate-induced strain in the resulting film to single crystals under very high pressure ($\sim$ 5.5 GPa) consistent with a key role of strong electronic correlation. They are confirmed by the measured high temperature maxima in both resistivity and Hall resistance. While hole-like charge carriers are inferred from the Hall effect measurements over the whole investigated temperature range, the Hall resistance reveals a non monotonic behavior at low temperatures that could be interpreted with an anomalous contribution. The resulting unconventional temperature dependence of the Hall resistance seems thus to combine high temperature strongly correlated features above 340 K and anomalous Hall effect at low temperature, below 100 K.Comment: Submitted to Physical Review B (2005

The structure of K- and Cs-monolayers on Cu(0 0 1): diffraction experiments far from the Bragg point

The intensity analysis along the crystal truncation rods has been used to analyse in situ the adsorption behaviour and the structure of K and Cs on Cu(0 0 1) at submonolayer coverages and room temperature. Up to about 0.25 ML K atoms adsorb in hollow sites followed by formation of a quasihexagonal superstructure. In contrast, for Cs adsorption the data can be interpreted by the formation of quasihexagonal Cs islands that grow with increasing coverage. For K an effective radius of 1.6(1) Å independent of coverage is determined. For Cs we fnd d = 2.1 (1) Å after formation of the quasihexagonal superstructure

Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface

We report magneto-transport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors, is difficult to reconcile with non-interacting electron theory.Comment: 4 pages, 4 figures, to appear in Physical Review Letter

An information adaptive system study report and development plan

The purpose of the information adaptive system (IAS) study was to determine how some selected Earth resource applications may be processed onboard a spacecraft and to provide a detailed preliminary IAS design for these applications. Detailed investigations of a number of applications were conducted with regard to IAS and three were selected for further analysis. Areas of future research and development include algorithmic specifications, system design specifications, and IAS recommended time lines