by Wong Woon-chung Jonathan. / Bibliography: leaves 232-260 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

Thesis (M.S.)--Oregon State University, 1985. / One map and one ill. folded in pocket. Typescript (photocopy). Includes bibliographical references (leaves 119-127). Also available online.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Mar. 18, 2010). Bibliography: leaves 55-58.

An ash monitoring system prototype that consists of a “clean” heat flux sensor and a “dirty” heat flux sensor was developed in this study. The “clean” heat flux sensor was studied numerically and experimentally while the “dirty” heat flux sensor was tested in the experiment. Two different measurement methods were applied on the “clean” sensor, one from the original study and one proposed in the present work. The new method required additional data processing procedures to be able to work in an on-line basis. Among the three data processing procedures developed in this study the central temperature difference procedure was found to be the most reliable one. Numerical results provided valuable information about the heat transfer pattern at the sensing element and also the performance of the sensor at high radiation heat flux levels. A rough calibration of both “clean” and “dirty” heat flux sensors was conducted experimentally. Nevertheless, the experimental results still served as a primary assessment for both sensors. Observed disagreements between the original study and the present one were probably caused by the modification of the sensor structure made in the present study. Sensitivity variation at high heat flux levels did not appear in the numerical results of either measurement method. Low overall sensor temperature change was believed to be the main reason as it meant less change in thermal properties of the sensing disc. Although the results of the study suggested that the proposed oscillation method was less attractive than the original one, it increased the possibility of resolving the surface characteristic variation problem that was considered crucial for the performances of the “clean” heat flux sensor regardless of the measurement method used. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-09-03 16:38:26.48

Phreatomagmatic eruptions result from the explosive interaction between magma and some external source of water, and produce deposits which are usually distinctive in nature from those of magmatic eruptions. The widespread deposits of large-scale phreatomagmatic eruptions (usually termed Phreatoplinian) are poorly studied relative to their magmatic counterparts and, consequently, current models for large-scale phreatomagmatic volcanism remain speculative. The Hatepe ash and Rotongaio ash (units 3 and 4 of the 1.85 ka Taupo eruption) are two classical widespread phreatomagmatic fall deposits. These have been examined in fine detail and sampled, for the first time, at a mm-scale, with the intention of quantifying vertical and lateral variations within these deposits and improving our understanding of the eruptive mechanisms and depositional processes during large-scale 'wet' eruptions. The Hatepe ash (1.75 km3) is a widespread (>15 000 km2, individual subunit bt values = 4.4 to 5.5 km), multiple-bedded, poorly-sorted pumiceous fall deposit. The fines-rich character and widespread occurrence of ash aggregates in the proximal to medial dispersal areas are indicators of a phreatomagmatic origin. Subunits contain multiple layers with a wide range of dispersal and grain size characteristics, and a number of distinctive primary lithofacies have been defined which characterise the changes in eruptive conditions and main depositional modes during Hatepe volcanism. The predominantly fine grained clasts (Mdø= 3.3-4.5), along with perhaps 20-25 wt.% liquid, were transported and deposited in the form of damp to wet 'mud lumps' and accretionary lapilli. Dispersal was from dense, 'wet' plumes which promoted the cohesion and aggregation of liquid-coated fine particles. This mode of transport and deposition was dominant during relatively long-lived episodes of relatively low discharge rate, with higher water/magma ratios at the vent and liquid/particle ratios in plumes. When magma discharge rate was relatively high and water/magma ratios low, fines-poor, plinian-style deposits (Mdø = -2.2 to 0.63) were produced by discrete particle fall from high (~25-30 km), relatively 'dry' plumes. Minor, short-lived fluctuations in discharge rate produced episodes of mixed discrete and ash aggregate fall which produced poly- and bimodal deposits (Mdø = 2.5-3) in proximal and inner-medial areas. Lateral emplacement by dilute, turbulent pyroclastic density currents was important in the proximal environment. The range and indices of Hatepe ash juvenile clast vesicularities (50-90%, and 75% vesicles, respectively) indicate that fragmentation was driven by magmatic volatiles but that water played some part in quenching. The minimal variation in juvenile clast vesicularity through the deposit and between the facies types indicates that the state of the Hatepe magma remained a uniform foam, and that the mechanism of fragmentation (but not the water/magma ratio) was consistent throughout Hatepe volcanism. Facies analysis and mapping of internal variations in ash dispersal confirm that the Hatepe ash is not the product of simple sustained magma discharge, but was actually the result of a continuous but highly irregular flux, with fluctuations in magma supply, sometimes over very short time intervals, resulting in a range of eruptive styles and depositional modes. The Rotongaio ash (0.8 km3) is a widespread (>10 000 km2, subunit bt values = 2.9 to 5km), poorly-sorted fall deposit with abundant evidence for the important involvement of liquid water at the vent and in the plume. Modes of deposition were similar to the Hatepe ash; dominantly damp to wet mud lump fallout (Mdø= 3.9 to 5.5), but with minor episodes of discrete particle fall (Mdø = -1.1 to 1.9) and mixed discrete and aggregate fall (Mdø= 1.2 to 2.9) caused by fluctuations in discharge rate. An additional depositional mode in medial areas during Rotongaio volcanism was by dilute, turbulent density currents, derived from particle-laden downbursts from the umbrella region of dense, wet, convectively-unstable plumes. Such a process may account for occurrences of cross-stratification in the medial-distal parts of other widespread ash falls. Secondary processes such as fluvial erosion and reworking, and soft-sediment deformation and slurry-flow were important depositional modes that operated syneruptively during Rotongaio (and Hatepe ash) volcanism. The very close association in time and space between primary and secondary lithofacies implies that there was a strong genetic link between the style of primary eruptive processes and the nature and extent of the secondary modification. In many cases the 'secondary' processes formed a continuum with primary depositional processes, influenced by the liquid/particle ratio of ash fallout and inherent to the mode of eruption. Throughout deposition of the Rotongaio ash a delicate balance always existed between primary accumulation, erosion and redeposition. The Rotongaio ash differs from the Hatepe ash, and most other widespread ash fall deposits, in a number of important ways which indicate the Rotongaio ash is not a typical phreatoplinian deposit; 1) it is extremely finely laminated in proximal exposures and many of these beds cannot be traced into the medial environment indicating it is the product of multiple, discrete and non-sustained explosions which dispersed material along a number of axes and with a wide range of thinning rates, 2) juvenile clasts are mostly poorly- to non-vesicular and clast populations span a very wide range of densities (0-65% vesicles) indicating that the Rotongaio magma was partially degassed and heterogeneous (unlike the Hatepe ash and other pumiceous phreatoplinian deposits), and fragmentation was driven not by vesiculation, but largely by external volatiles, 3) the lack of any significant coarse component compared to the Hatepe ash at anyone site supports a fundamentally different mode of fragmentation for Rotongaio volcanism and vent processes which probably involved significant recycling of clasts through the vent. Detailed analysis of the Hatepe ash and Rotongaio ash has provided some interesting insights into the nature of large-scale phreatomagmatic eruptions. Ash dispersal patterns for subunits of the two deposits indicate that 'wet' and 'dry' plumes, even of comparatively small magnitudes (0.02 to 0.8 km3 subunit volumes) behave in distinctive ways which hint at fundamentally different dynamics of dispersal. Assessment of lateral variations in clast size populations suggest the differences between proximal strongly fines-segregated 'dry' facies and the fines-rich 'wet' facies is an artefact controlled mostly by the initial liquid/solid ratio in the plume rather than the mechanism of fragmentation.

Most of the wastes in Sweden end up in incinerator plants. These trashes are full of metals, especially aluminium, which will not oxidize, they can’t always be recycled and they will instead oxidize in water and leak hydrogen gas to its surrounding. Estimations calculate it could be an average potential of around 40-50 kWh/ton of burnt trash. Ignoring the imported trash, the national recovery potential of Sweden’s 4,3 million tonnes of trash would then be equal to 170-220 GWh/year due to non-recyclable metals, which are currently going to temporary landfills. The requirements to harness this potential are technically simple, and can be achieved by a quick separation of the recyclables and the non-recyclables. This report will review the factors which increase the rate of reaction and study different ways of extracting the energy, by electrolysis, thermal treatment and mechanical mixing. This was done by taking small samples from the MSWI, owned by Umeå Energi AB, and putting them in small containers. While using the different methods, electrolysis, thermal treatment and mechanichal mixing, the amount of developed H2 gas over time was measured. The result shows that the best methods are mechanical mixing together with thermal treatment, where mechanical mixing seems to give the biggest effect of them two. The electrolysis did not work as intended, where there could be issues with the conductivity of the ash-mixture.

Although numerous hazard models exist to assess possible ash fallout from explosive volcanic eruptions around the world, these models frequently neglect to consider ash aggregation or use a simple percent proxy to represent aggregation, without considering the varying processes at work throughout the volcanic flow. Eruption dynamics are sensitive to ash aggregation, and ash aggregates are commonly found in eruptive deposits, yet few experiments have been conducted on aggregation phenomena using natural materials. In this work, experiments were developed to produce both probabilistic and process-based relationships for the efficiency of ash aggregation with respect particle size, collision kinetic energy, atmospheric water vapor and residence time. A synthetic ash proxy, ballotini, and ash from the 2006 eruption of Tungurahua, Ecuador, and the 1980 eruption of Mount St. Helens, WA, were examined for their aggregation potential. Two aggregation regimes, wet and dry, were identified based on their potential for aggregation. The wet flow regime occurs when particles are circulated in high relative humidity environments long enough to develop a water layer with a thickness that exceeds the particle roughness scale. Hydrodynamic forces control aggregation in the wet flow regime. The dry flow regime includes particles in low relative humidity environments as well as those that circulate too briefly in high humidity environments to fully develop a water layer. Electrostatic forces control aggregation in the dry flow regime. Aggregation efficiency in both regimes was dominantly controlled by collision kinetic energy; however, this effect is significantly dampened in the wet flow regime. Equations governing the relationships between aggregation efficiency, collision kinetic energy and the related forcings in the wet or dry flow regimes have been developed for implementation into large-scale numerical volcanic models. The results of this experimental work have been developed into a probability distribution that has been integrated and incorporated into a multifluid numerical model. The numerical simulation was tested on a range of explosive depths and overpressure estimates from the 1790 eruption of Kilauea volcano, HI. The model output was compared to field data collected on the deposit thickness moving away from the source and the distribution, including both size and density, of aggregates. The mass fraction of ash removed from the eruption column in the form of aggregates was also calculated to examine how efficiently aggregation processes remove ash throughout the eruption. Cumulatively, the work presented here furthers our understanding of aggregation processes and the role they play in volcanic eruptions.

Graduation date: 1985

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1916. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 2, 2009)

Thesis (M.S.)--University of North Texas, Dec., 2009. / Title from title page display. Includes bibliographical references.