The thesis is concerned with some of the properties of positive and negative ions in liquid Helium, and in particular with the passage of ions, which are generated inside the liquid, through the free liquid surface into vapour. It was found, for negative ions, that this process was inhibited by an energy barrier, in agreement with other workers who have examined this problem, although there is considerable disagreement as to the magnitude of the barrier. It has been observed in the present work that the energy barrier depends upon the field, the position of the liquid surface in an ion cell, and the nature of the ion cell itself. The dependence of the barrier on these three parameters probably explains why diverse values for it have been reported. It was originally intended to use the ions as probes to examine dissipation mechanisms in the mobile superfluid Helium film. It had been reliably reported that ions preferentially travelled in the film. This was observed not to be the case however. The negative ion currents sin the film were found to be extremely small, when they existed at all, and no real positive ion currents in the film could be detected. This has been interpreted as being due to the combination of the large image potential binding the ion to the substrate, and the intrinsic roughness of the substrate. The present work has revealed that what appears at first sight to be a current of positive ions crossing the liquid surface can be attributed to a current of photoelectrons due to photoelectric emission from the surface of the collector. Such photoemission can arise from the uv radiation produced largely by ionic recombination in the region close to the a-emitting source. Screening the collector from the direct view of the a-source greatly reduced the photoelectron current. In order to extend the temperature range available, for the study of ion currents, a vortex refrigerator was designed and constructed. This enabled measurements to be extended down to 0.8K. Since there has been only one publication on the vortex refrigerator, which appeared during the building of the present one, its properties and operation with various design parameters were studied in detail.

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The processes associated with magma injection at shallow depths within the crust have been the topic of many geophysical studies, some investigating the seismicity that accompanies volcanic activity and others attempting to map the subsurface extent and geometry of the resulting magma bodies. The aim of this study is to obtain a better understanding of these processes by investigating the nature of seismic signals that accompany volcanic eruptions and by seismically imaging a magma body beneath a mid-ocean ridge, both located on, or adjacent to Iceland. The seismic phenomena associated with the 1996 Vatnajӧkull subglacial eruption in central Iceland, have been studied using data recorded by both temporary (HOTSPOT) and permanent (SIL) seismic networks. These networks comprise 60 broadband and short-period three-component seismographs and cover most parts of the country. Two very active volcanic systems, Bárdarbunga and Grimsvӧtn, are situated underneath the Vatnajokull ice cap. The volcanoseismic signals recorded there were categorised according to their waveform shape and frequency content, into three groups: (a) low-frequency events (1-2 Hz); (b) mixed-frequency events (1-4 Hz); and (c) volcanic tremor. The eruption was preceded by intense seismic activity which began with a = 5.6 earthquake located at the Bárdarbunga volcanic system. The epicentres of the earthquake swarm that followed the M(_w), = 5.6 event initially delineated the Bárdarbunga caldera rim and then migrated towards Grimsvӧtn, to a place where a fissure was later observed. Pre-eruptive tremor started at least two days before the eruption as a harmonic signal around five narrow frequency bands (0.5-0.7, 1.6, 2.2, 2.8 and 3.2 Hz). Co-eruptive tremor started as a broadband, continuous signal which evolved into low-amplitude background tremor interrupted by high-amplitude, cigar-shaped bursts. Further analysis revealed that continuous tremor and the cigar-shaped bursts had all the characteristics of low- dimensional chaotic signals. Geophysical and geochemical evidence suggest that a lateral migration of magma from Bárdarbunga facilitated the rupture of the roof of a magma chamber, situated at the fissure area, which subsequently erupted as tephra on the glacier. The second phase of the RAMESSES (Reykjanes Ridge Axial Melt Experiment: Structural Synthesis from Electromagnetic and Seismics) experiment involved the acquisition of multichannel seismic reflection data from 39 along- and across-axis lines shot over the magmatically active 57º 45'N axial volcanic ridge. The data from one along-axis line were processed using a variety of techniques that mainly aimed at reducing the large amount of coherent noise present, a result of scattered energy at the rough seabed. The final processed section revealed a number of reflection events that could be interpreted as intra-crustal reflections, originating from the interface between pillow lavas and sheeted dykes, and from the top part of a thin melt lens.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Chung, Chor Fung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 95-97). / Abstracts in English and Chinese. / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.xiii / Nomenclature --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Development of Micro Indoor Surveillance Flyers --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Intrinsic Problem of Surveillance Helicopters --- p.2 / Chapter 1.2 --- Proposed Non-moving Parts and Noiseless Flyers --- p.2 / Chapter 1.3 --- Organization of the remaining dissertation --- p.5 / Chapter Chapter 2 --- The Basic Structure of the Ionic Flyers --- p.7 / Chapter 2.1 --- The Components and the Structural Parameters of the Ionic Flyers --- p.7 / Chapter 2.2 --- Proposed Operational Principles --- p.8 / Chapter 2.2.1 --- The Electrohydrodynamic Effect --- p.9 / Chapter 2.2.2 --- The Biefeld-Brown Effect --- p.10 / Chapter Chapter 3 --- Overview of Corona Discharge --- p.11 / Chapter 3.1 --- The Gaseous Discharge --- p.11 / Chapter 3.2 --- "Uniform Fields, Electrical Breakdown" --- p.12 / Chapter 3.3 --- "Non-uniform Fields, Corona Discharge" --- p.12 / Chapter 3.3.1 --- Positive Corona Discharge --- p.13 / Chapter 3.3.2 --- Negative Corona Discharge --- p.14 / Chapter 3.4 --- Conclusion --- p.15 / Chapter Chapter 4 --- Electrical Current-Voltage Model --- p.16 / Chapter 4.1 --- Experimental Setup and Measurement --- p.17 / Chapter 4.2 --- Basic Current to Voltage Relationship --- p.18 / Chapter 4.2.1 --- The Three Electrical Stages of the Ionic Flyers --- p.20 / Chapter 4.2.2 --- Proposed Quadratic Equation for the Current to Voltage Relationship --- p.22 / Chapter 4.3 --- Determination of the Current Gain C and the Onset Voltage V0 by the Structural Parameters of the Ionic Flyers --- p.22 / Chapter 4.3.1 --- The Electrode Length (L) --- p.24 / Chapter 4.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.27 / Chapter 4.3.3 --- The Wire-emitter Radius (rw) --- p.31 / Chapter 4.3.4 --- The Plate-collector Height (h) --- p.36 / Chapter 4.3.5 --- The Electrode Enclosed Area (A) --- p.38 / Chapter 4.3.6 --- The Electrical Environmental Constant (Ke) --- p.43 / Chapter 4.4 --- Summary of the Experimental Derived Current-Voltage Model --- p.45 / Chapter Chapter 5 --- Mechanical Lift-force Models --- p.46 / Chapter 5.1 --- Experimental Setup and Measurement --- p.47 / Chapter 5.2 --- Basic Lift-force to Voltage Relationship --- p.49 / Chapter 5.2.1 --- The Initial Power Dissipation (IPD) --- p.50 / Chapter 5.2.2 --- The Maximum Lift-force --- p.51 / Chapter 5.2.3 --- Proposed Third-order Equation for the Lift-force to Power Relationship --- p.52 / Chapter 5.3 --- Determination of the Voltage Gain J and the Barrier Voltage Vfby the Structural Parameters of the Ionic Flyers --- p.54 / Chapter 5.3.1 --- The Electrical Length (L) --- p.55 / Chapter 5.3.2 --- The Gap Distance between the Wire-emitter and the Plate-collector (d) --- p.59 / Chapter 5.3.3 --- The Wire-emitter Radius (rw) --- p.63 / Chapter 5.3.4 --- The Plate-collector Height (h) --- p.66 / Chapter 5.3.5 --- The Electrode Enclosed Area (A) --- p.67 / Chapter 5.3.6 --- The Lift-force Environmental Constant (Kf) --- p.71 / Chapter 5.4 --- Summary of the Experimental Derived Lift-force Model --- p.73 / Chapter 5.5 --- Analysis on the Force/Power Ratio of the Ionic Flyers --- p.74 / Chapter Chapter 6 --- Further development of the Ionic Flyers --- p.76 / Chapter 6.1 --- Multi-directional Force Generation --- p.76 / Chapter 6.1.1 --- Linear Motion --- p.77 / Chapter 6.1.2 --- Rotation Motion --- p.78 / Chapter 6.2 --- Application of MEMS Motion Sensors and Wireless Signal Transmission --- p.80 / Chapter Chapter 7 --- Future Work --- p.84 / Chapter 7.1 --- Single-Emitter-Multiple-Collector Ionic Flyers --- p.84 / Chapter 7.2 --- Development of Miniaturized High-voltage Power Supply --- p.88 / Chapter Chapter 8 --- Conclusion --- p.90 / Chapter 8.1 --- The Electrical Current to Voltage Model --- p.90 / Chapter 8.2 --- The Mechanical Lift-force to Power Model --- p.91 / Chapter 8.3 --- The Force/Power Ratio Model --- p.91 / Appendix A --- p.92