Experimental data are reported for solids suspension and distribution in four geometrically similar vessels with diameters equal to 0.31, 0.61, 1.83 and 2.67 m. Agitation was provided by a series of pitched blade turbines with impeller to vessel diameter ratios from 0.3 to 0.6 and pitched angles between 30° and 90°. The effect of impeller clearance on solids suspension was examined for a clearance range of T/4 to T/8. Dual impeller systems were also studied, covering two combinations (dual pitched and flat/pitched) and impeller spacing of half to two diameters apart. The majority of the experiments were carried out with 150-210 μm round-grained sand (density: 2630 kg ‭m-3 and settling velocity: 0.015 m s-1) and tap water. Solids concentration was varied between 0.1 to 40% by weight. Four parameters were measured; impeller speed, using an optical tachometer, power input, calculated from the shaft torque given by strain gauges, just suspension speed, ascertained both visually and by use of an ultrasonic Doppler flowmetering (UDF) technique and the local solids concentration, measured by a in-house solids concentration probe. In addition extensive flow visualisations were made with the 0.61 m vessel in order to establish both liquid and particles flow patterns during the experiments. Results from this study were compared with previous publications in order to examine the effects of some of the important geometrical variables on solids suspension and distribution. This work revealed that for the range of parameters covered, the smallest (D/T=0.3) and the largest (D/T=0.6) impellers are the most and least efficient ones for solids suspension. Distribution tests with the three geometrically similar impellers show that the results are neither correlated in terms of tip speed nor power input but are best described by the thrust force generated by the impellers. In general, dual impeller systems improve solids distribution but require more power to just suspend solids compared with a single impeller. The scaling effect proposed by Zwietering (1958) for solids suspension has been confirmed by this study for vessel up to 2.67 m in diameter. The constant tip speed rule for solids distribution, which is based on one-dimensional dispersion models was found to underestimate the power requirement in large scale applications. This study indicates that equal power per unit volume is required to achieve the same degree of homogeneity.

No description available.

No description available.

No description available.

The distribution of Phanerozoic sediment-hosted mineral deposits appears to be influenced by latitudinal zoning. The palaeolatitudes of the host rocks were determined using standard palaeomagnetic procedures - the most reliable results being for the Mesozoic and Cenozoic with early Palaeozoic palaeolatitudes least reliable. The palaeolatitudes derived from Tarling and BP palaeogeographic reconstructions are in general agreement i. e. +/- 10°, although greater discrepancies occur for India and Central America. It is shown that some types (e. g. sandstone copper, sandstone lead) have a preference for low latitude arid regions whilst conditions in the equatorial and temperate rainfall belts were more favourable to the formation of other deposits (e. g. sandstone uranium-vanadium, oolitic ironstone). Using climatic modelling assuming uniformitarianism of the principles governing the Earth's atmospheric and oceanic circulation patterns, the climatic conditions affecting the distributions of sediment-hosted deposits were evaluated. It is concluded that local climatic effects are influential in the genesis of limestone base-metal, oolitic ironstone, sandstone copper, sandstone lead, shale base-metal, sedimentary exhalative, sandstone uranium-vanadium, manganese, laterite and phosphate deposits. These climatic conditions affect the nature and degree of chemical weathering, erosion, abundance of organic matter, ground water chemistry and volume in a particular region. However in some instances, such as placer deposits, the major control on deposit distribution was the availability and distribution of source rocks. Such palaeolatitudinal/palaeoclimatic control on the distribution of some deposit types places genetic constraints upon their formation. It also has obvious implications in the evaluation of potential sites for exploration and development.

No description available.

No description available.

In this thesis we develop practical tools for quantum key distribution (QKD) security proofs. We apply the tools to provide security proofs for several protocols, ranging from discrete variable protocols in high dimensions, protocols with realistic implementations, measurement device independent QKD and continuous-variable QKD. The security proofs are based on the Devetak-Winter security framework [I. Devetak and A. Winter, Proc. of the Roy. Soc. of London Series A, 461, 207 (2005); B. Kraus, N. Gisin, and R. Renner, Phys. Rev. Lett., 95 080501 (2005)]. In the key rate calculation, it is often convenient to assume that the optimal attack is symmetric. Under the assumption that the parameter estimation is based on coarse-grained observations, we show that the optimal attack is symmetric, if the protocol and the postselection have sufficient symmetries. As an example we calculate the key rates of protocols using 2, d and d+1 mutually unbiased bases in d-dimensional Hilbert spaces. We investigate the connection between the optimal collective eavesdropping attack and the optimal cloning attack, in which the eavesdropper employs an optimal cloner to attack the protocol. We find that, in general, it does not hold that the optimal attack is an optimal cloner. However, there are classes of protocols, for which we can identify the optimal attack by an optimal cloner. We analyze protocols with mutually unbiased bases in d dimensions, and show that for the protocols with 2 and d+1 mutually unbiased bases the optimal attack is an optimal cloner, but for the protocols with d mutually unbiased bases, it is not. In optical implementations of the phase-encoded BB84 protocol, the bit information is usually encoded in the phase of two consecutive photon pulses generated in a Mach-Zehnder interferometer. In the actual experimental realization, the loss in the arms of the Mach-Zehnder interferometer is not balanced, for example because only one arm contains a lossy phase modulator. Since the imbalance changes the structure of the signals states and measurements, the BB84 security analysis no longer applies in this scenario. We provide a security proof for the unbalanced phase-encoded BB84. The loss does lower the key rate compared to a protocol without loss. However, for a realistic parameter regime, the same key rate is found by applying the original BB84 security analysis. Recently, the security of a measurement device-independent QKD setup with BB84 signal states was proven in Refs. [H.-K. Lo, M. Curty, and B. Qi, Phys. Rev. Lett., 108 (2012); S. L. Braunstein and S. Pirandola, Phys. Rev. Lett., 108 (2012)]. In this setup Alice and Bob send quantum states to an intermediate node, which performs the measurement, and is assumed to be controlled by Eve. We analyze the security of a measurement device-independent QKD protocol with B92 signal states, and calculate the key rates numerically for a realistic implementation. Based on our security proof we were able to prove the security of the strong reference pulse B92 protocol. We analyze the security of continuous-variable protocols using the entropic uncertainty relations established in Ref. [M. Berta, M. Christandl, R. Colbeck, J. M. Renes, and R. Renner, Nature Physics 6, 659 (2010)] to provide an estimate of the key rate based on the observed first and second moments. We analyze a protocol with squeezed coherent states and the 2-state protocol with two coherent states with opposite phases.

Photocopy of typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1978. / Bibliography: leaves 175-177. / Microfiche. / vii, 177 leaves 28 cm

No description available.