A new dewatering technology, called low temperature drying, has been developed to remove water from ultrafine (minus 325 mesh) coal particles. The process subjects partially dewatered solids to intense mechanical shearing in the presence of unsaturated air. Theoretical analysis of the thermodynamic properties of water indicates residual surface moisture should spontaneously evaporate under these conditions. This is contingent on the large surface area of these fine particles being adequately exposed to an unsaturated stream of air. To demonstrate this process, three dispersion methods were selected for bench-scale testing; the static breaker, air jet conveyor, and centrifugal fan. Each of these devices was chosen for its ability to fully disperse and pneumatically convey the feed cake. The moisture content of the feed cake, and the temperature and relative humidity of the process air were the key parameters that most significantly affected dryer performance. Of the three methods tested, the centrifugal fan produced the best results. The fan was capable of handling feeds as wet as 21.5% and consistently dried the coal fines below 2% moisture. The cost of the air and heat required to provide good drying performance was modeled to explore the practicality of the drying process. Modeling was accomplished by modifying equations developed for thermal dryers. The modeling results indicate, if good exposure of the fine particle surface area is achieved, dryers operating with either heated or unheated (ambient) air can be used for drying ultrafine coal. / Master of Science

<p> This thesis reports on the investigation of damage production in GaAs at low temperature using the channeling-backscattering technique.</p> <p> The study has been divided into two parts; first, the investigation of damage produced by 2 MeV helium ions in unimplanted and previously implanted samples with varied doses of 40 keV nitrogen and bismuth. The helium beam damage has been found to depend on the initial state of damage of the samples. In the second part the damage production due to 40 keV N+, As+, Sb+ and Bi+ ion implantation has been investigated. A comparison with damage production due to the corresponding 80 keV diatomic implants has also been carried out. No enhancement in the damage production was noticed due to the molecular implants.</p> / Thesis / Master of Engineering (MEngr)

No description available.

The current rice varieties grown by Australian farmers are susceptible to low temperature events particularly during the reproductive stage of plant development. The best management practices of sowing within the recommended time period and maintaining deep water (20–25 cm) through the microspore development stage only offer limited protection. There is a need to develop more cold tolerant varieties and to do so requires the development of low-temperature screening capacity for the NSW rice breeding program. This study looked at the requirements of adapting a controlled-temperature glasshouse facility to enable screening for tolerance to low temperatures during the reproductive stage of rice development. The investigations were grouped into two areas; 1) the physical aspects of the low temperature facility including the location of plants within the facility and within the tubs used to grow the plants and whether these can influence the reliability of the screening and 2) the biological effects of nitrogen (N) concentration in the plant at panicle initiation (PI) and plant susceptibility to low temperatures, and whether growth stage of the plant relative to PI at the start of low temperature treatment influenced floret sterility. A series of nine experiments were conducted at the Deniliquin Agricultural Research and Advisory Station glasshouse facility using up to five rice varieties selected for their divergence in low-temperature tolerance. One other experiment was conducted in a different facility. The modified glasshouse facility in Deniliquin was effective in providing the targeted screening environment of 27°C day and 13°C night temperature regime. There was however a smaller than expected effect of the low temperature exposure in some of the experiments with sterility following low temperature ranging from 9.9% to 27.7%. There was also a higher than expected level of sterility in the controls (i.e. not exposed to low temperature) with sterility levels up to 58% recorded in one experiment. The causes of these overall effects are not known. Notwithstanding these overall effects there were a number of findings that are important for developing a reliable screening facility. The spatial arrangement of the plants within the low temperature facility effected the level of sterility highlighting the need for experimental design to consider spatial variation. The existence of edge effects was identified within the tubs used to maintain permanent water on the potted plants whereby the outer plants in the tubs were less damaged by the low-temperature treatment. The overall N level in the leaf tissue was low even at the equivalent rate of 250 kg N ha-1 and there was only a very modest and inconsistent response in N concentration at PI to N application rates ranging from 0 to 250 kg ha-1. However, the method of growing the plants in pots and of nitrogen fertiliser application did not alter the N concentration. The concentration was the same when N was added either, on the same day as permanent water application, or three days prior to permanent water application. Also restricting the direction of water movement through the pots and therefore the soil within the pots did not alter the amount of N in the plants at PI. The low plant N concentrations were consistent across two glasshouses in which soil from the same source was used suggesting a soil limitation. A soil test identified that the soil phosphorus (P) was at a level at which plants have responded to P application under field conditions, and the loamy texture of the soil had an associated low cation exchange capacity in comparison to medium to heavy clay soil types commonly associated with rice growing. These factors may have reduced the N retention and uptake and, in part, explain the low injury from the low temperature exposures. In the variety Millin, there was no significant effect of timing of the exposure on sterility until it commenced 12 to 15 days after PI. This is a significant finding for a breeding program that must expose lines of unknown phenological development. It means that even though there are small differences in the rates of development, there is no large effect of this on sterility. However, this response was not seen in the other varieties tested and thus requires further validation. It was difficult to induce repeatable levels of floret sterility in this series of experiments most likely due to the low N concentrations in part due to the properties of the soil used to grow the plants. This highlights the importance of standardising all cultural aspects in order to provide uniform and repeatable screening information. The spatial effects highlight importance of experimental design for effective exposure to low temperature treatments, incorporation of the capacity for spatial analysis in the statistical design, the use of standard variety checks for floret sterility after low temperature treatment, and the determination of N concentration in plant tissue prior to exposure.

No description available.

No description available.

Robust interpretations of rock thermal histories are critical for resolving the timing and rates of geologic processes, especially as low-temperature thermochronology has become a common tool for investigating the evolution of landscapes and mountain belts and the feedbacks between geodynamic processes. Most interpretations of thermochronologic cooling ages, however, attribute rock cooling entirely to rock exhumation - a common but tenuous assumption in many settings where thermochronology is used to investigate links between tectonics, climate, and landscape evolution, because these places often have history of magmatism. Exploring the complexities - and advantages - of interpreting low-temperature thermochronologic data in magmatic terranes is the principal theme of this work. Using simple analytical approximations as well as the finite-element code Pecube, we characterize the cooling age patterns inside and around plutons emplaced at upper and middle crustal levels and identify the advective and conductive scaling relationships that govern these patterns. We find that the resetting aureole width, the difference between reset and unreset cooling ages in country rocks, and the lag time between pluton crystallization age and pluton cooling age all scale with exhumation rate because this rate sets the advective timescale of cooling. Cooling age-elevation relationships in these steadily exhuming models have changes in slope that would masquerade as changes in exhumation or erosion rates in real datasets, if the thermal effects of the plutons were not accounted for. This is the case both in the country rocks immediately next to upper crustal plutons and, surprisingly, in the country rocks kilometers above mid-crustal plutons with no surface expression. Together with a lag-time analysis useful for the practical question of when it is appropriate to interpret a cooling age as an exhumation rate in crystalline rocks, this work improves our framework for evaluating the effects of magmatism on thermochronologic datasets. We also demonstrate the importance of considering the magmatic history of a region in field studies of the Colorado Plateau, where interpreting apatite (U-Th)/He data requires diagnosing significant inter- and intra-sample age variability. Prior to considering the thermal history of the region, we develop a new model for a common source of this age variability: excess He implantation from U and Th (i.e., eU) hosted in secondary grain boundary phases (GBPs), which can make very low eU apatites hundreds of percent 'too old'. Samples significantly affected by He implantation are not useful for thermal history interpretations, but this model does provide a diagnostic tool for discriminating these samples from those with useful age trends. Once the effects of GBPs have been accounted for, the remaining data from two different thermochronologic archives in the central Colorado Plateau provide a new perspective on the Cenozoic history of the region, which has a multiphase - and enigmatic - history of magmatism and erosion. We find that sandstones in the thermal aureoles around the Henry, La Sal, and Abajo mountains intrusive complexes were usefully primed by magmatic heating in the Oligocene to document the subsequent late Cenozoic history of the region more clearly than any other thermochronologic archive on the Plateau. These data document a stable Miocene landscape (erosion rates<30 m/Ma) that rapidly exhumed ~1.5-2 km in the Plio-Pleistocene (~250-700 m/Ma no earlier than 5 Ma) in the Henry and Abajo mountains, and strongly suggest most of this erosion occurred in the last 3-2 Ma. The integration of the Colorado River ca. 6 Ma, which dropped regional base-level, is the principal driver of this erosion. It is likely, however, that a component of the rapid Pleistocene rock cooling is unique to the high mountains of the Colorado Plateau and reflects an increase in spring snow-melt discharge during glacial periods. Although apatite thermochronology results far from the Oligocene intrusive complexes cannot resolve this detailed Plio-Pleistocene history, they do constrain the onset of late Cenozoic erosion to no earlier than ~6 Ma. Moreover, apatite cooling ages from these rocks also document Oligocene cooling (ca. 25 Ma) that is contemporaneous with the emplacement of the laccoliths and the waning of the vigorous magmatic flare-up that swept through the southwestern USA ca. 40-25 Ma. Although the cooling ages are consistent with ~1 km of exhumation in the late Oligocene and early Miocene, as previous workers have suggested in the eastern Grand Canyon region, we demonstrate that a transient change in the geothermal gradient (peaking at ~50˚C/Ma in the late Oligocene) driven by moderate mid-crustal magmatism can produce identical age patterns. Therefore, we re-interpret the mid-Cenozoic erosion event on the Colorado Plateau as primarily a change in the crustal thermal field, rather than an erosional event. This requires a more significant Laramide-age unroofing in parts of the central Plateau and perhaps a re-evaluation of the interpretations of Oligocene canyon cutting in the Grand Canyon region

No description available.

No description available.

by Leung Chu Wah. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 181-182). / Acknowledgements --- p.vi / Abstract --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Evaluation of Far Field by Lai and Char's Method --- p.6 / Chapter 2.1 --- Far Field Expression --- p.6 / Chapter 2.2 --- Radiation Power --- p.12 / Chapter 2.3 --- Gaussian Curvature and Point of Stationary Phase of Cylindrically Symmetry DWS --- p.16 / Figures for Chapter2 --- p.19 / Chapter 3. --- Synchrotron Radiation in Vacuum Using Lai and Char's Method --- p.20 / Chapter 3.1 --- The Far Field --- p.20 / Chapter 3.2 --- Current Density for a Gyrating Charge --- p.22 / Chapter 3.3 --- Radiation Power --- p.25 / Chapter 3.4 --- Some Angular Properties of Synchrotron Radiation --- p.29 / Chapter 3.5 --- Total Power Emitted in N-th Harmonic --- p.32 / Chapter 3.6 --- Total Power Emitted in All Harmonics --- p.33 / Figures for Chapter3 --- p.36 / Chapter 4. --- Synchrotron Radiation in a Cold Magnetoplasma --- p.42 / Chapter 4.1 --- DWS for a Cold Magnetoplasma --- p.42 / Chapter 4.2 --- Derivatives of kp and Gaussian Curvature of DWS --- p.45 / Chapter 4.3 --- Group Velocity --- p.46 / Chapter 4.4 --- Current Density --- p.47 / Chapter 4.5 --- Point of Stationary Phase --- p.48 / Chapter 4.6 --- Identification of Different Wave Modes --- p.48 / Chapter 4.7 --- Radiation Power --- p.49 / Chapter 4.8 --- Relation with Vacuum Case --- p.53 / Figures for Chapter4 --- p.56 / Chapter 5. --- Incoherent Radiation from an Assembly of Charges --- p.79 / Chapter 5.1 --- Total Incoherent Energy Flux from N Particles --- p.79 / Chapter 5.2 --- Synchrotron Radiation from Particles with Momentum Distribution --- p.80 / Chapter 5.3 --- Mono-Energetic Particles with Distributed Parallel Momentum --- p.82 / Chapter 5.4 --- "Angular Distribution, Frequency Distribution and Total Radiation Power" --- p.87 / Figures for Chapter5 --- p.88 / Chapter 6. --- Coherent Radiation from an Assembly of Charges --- p.94 / Chapter 6.1 --- Bunching Factor --- p.94 / Chapter 6.2 --- Some Arrangements of Particles --- p.96 / Chapter 6.2.1 --- Charges Distributed Uniformly over an Arc of Angular Width --- p.96 / Chapter 6.2.2 --- Charges Distributed Along a Straight Line --- p.100 / Chapter 6.2.3 --- Charges Distributed Uniformly on a Helical Path --- p.101 / Chapter 6.2.4 --- Charges Distributed Randomly on an Arc --- p.102 / Chapter 6.3 --- Effect of Bunching in a Cold Magnetoplasma --- p.104 / Figures for Chapter6 --- p.105 / Chapter 7. --- Correction to Radiation Power Formula for Degenerate DWS --- p.113 / Chapter 7.1 --- Far Field Expression for Degenerate DWS --- p.113 / Chapter 7.2 --- Radiation Power for Degenerate DWS --- p.115 / Chapter 7.3 --- Alternate Proof for the Extra Factorin (7.2.11) --- p.118 / Chapter 7.4 --- Example of Degenerate DWS - Vacuum --- p.120 / Chapter 8. --- "Ratio of Emitted Power to Received Power, f" --- p.122 / Chapter 8.1 --- Group Velocity in terms of Derivatives of DWS --- p.122 / Chapter 8.2 --- Calculation of Derivatives --- p.124 / Chapter 8.3 --- Expression for f --- p.126 / Chapter 8.4 --- Alternate Form of f --- p.127 / Chapter 8.5 --- Examples of Calculating f Using (8.4.1) --- p.129 / Chapter 8.5.1 --- Isotropic Cold Plasma --- p.129 / Chapter 8.5.2 --- Cold Magnetoplasma --- p.130 / Figures for Chapter8 --- p.132 / Chapter 9. --- Comparison of Far Field by Lai and Chan with that by Others --- p.135 / Chapter 9.1 --- Expressing the Far Field Ratio in terms of Derivatives of DWS and WS --- p.135 / Chapter 9.2 --- Far Field Ratio for an Uniaxial Non-Dispersive Medium --- p.137 / Chapter 9.3 --- Far Field Ratio for an Isotropic Cold Plasma --- p.138 / Chapter 10. --- Minimum Far Field Distance to a Moving Radiating Source in an Anisotropic and Dispersive Medium --- p.140 / Chapter 10.1 --- Sub-Dominant Terms of the Far Field --- p.141 / Chapter 10.2 --- Minimum Far Field Distance --- p.147 / Chapter 10.3 --- Minimum Far Field Distance in an Isotropic Non-Dispersive Medium --- p.152 / Chapter 10.4 --- Minimum Far Field Distance in an Isotropic Dispersive Cold Plasma --- p.156 / Chapter 10.5 --- Minimum Far Field Distance for Alfven Waves in a Cold Magnetoplasma --- p.159 / Chapter 10.6 --- Comparison of Results by Other Authors --- p.162 / Figures for Chapter 10 --- p.165 / Chapter 11. --- Conclusions / Chapter Appendix 1. --- Calculation of the Total Power Emitted in Synchrotron Radiation in Vacuum --- p.170 / Chapter Appendix 2. --- "Derivatives of stix's Parameters and a1,a2 of Equation (4.1.22)-(4.1.23 )" --- p.176 / Chapter Appendix 3. --- Dispersion Relation for Alfven Wavesin a Cold Magnetoplasma --- p.179 / References --- p.181