This thesis presents the design and construction of a low temperature differential (LTD) Stirling engine for electric power generation. The target energy sources were geothermal, industrial waste heat or solar heated water. These sources would supply a source temperature of around 90 °C. Assuming that the sink is kept at around 20 °C, the engine was designed based on a temperature difference of approximately 70 °C. The initial design and basic structure of the engine was completed in a previous project utilising first order design methods. The goal was to develop a low cost prototype engine capable of producing up to 500W electrical output power. A novel gamma type engine was proposed utilising a rotary reciprocating displacer and industrial steam piping to form a low cost pressurised chamber. This project concentrated on advancing the design and construction towards completion with particular emphasis on the electrical control, measurement/instrumentation components, and gas flow through the regenerator. At the completion of this project the displacer piston actuation system has been redesigned. In order to achieve the displacer’s specified 2 ㎐ actuation, both the displacer’s structure and the actuation system were altered. The displacer’s aluminium shell and foam centre were removed and replaced with a pine superstructure coated in depron foam, reducing the moment of inertia from 0.4488 ㎏ ∙ ㎡ to 0.0984 ㎏ ∙ ㎡. A secondary motor was added to the actuation system to increase the actuation power. The gearing ratio was also altered from 10:1 to 2:1 to increase the peak displacer speed. The regenerator was designed and built to suit the unusual wedge shape requirements of the original design. A ribbed structure was conceived to allow fluid flow to be manipulated within separate sections, producing an even pressure drop over varying regenerator lengths. Simulations were run to optimise both the number of sections and the mass of wire wool to be placed in each segment. The final regenerator design has axial ribs placed at radii of 93, 134, 192, 276 and 392mm, creating four sections. These sections are filled with 0.68, 0.97, 1.40 and 1.90kg of #0 mild steel wire wool. As Stirling engines are not self-starting the generator was required to be run as a motor when starting the Stirling engine. To achieve bidirectional flow of current within the starter motor/generator control system, a field oriented control (FOC) inverter from Texas Instruments was purchased and set up to run the 1kW, 3 phase, permanent magnet generator in both motor and generation modes. This will allow the Stirling engine to be brought up to speed with the generator operating as a motor and then switch to generation mode when the motoring current falls below a set limit. Both pressure and temperature measurement systems were developed, constructed and tested in order to collect information about the performance of the engine under operation. Three pressure transducer circuits were designed and constructed with measurement ranges of 10 ㎪, ±0.99 ㎪ and ±6.66 ㎪. These circuits were integrated with a PiocLog1012 analog to digital converter and PicoLog recording software. Eight K-type thermocouples were used for temperature recording. These were sampled with a Pico Technology TC-08 temperature thermocouple data logger which in turn was connected, via USB, to a computer running PicoLog Recorder software. Thus far all component testing has been carried out with test rigs that model the relevant parts of the engine. The displacer actuation system and phase angle control of the displacer and power piston has been tested. Temperature and pressure measurement systems have been independently tested. Motor/generator speed control and switching has been simulated and tested. Unfortunately completion of the engine assembly was not achieved within the scope of this project and therefore fully integrated testing of all components was not carried out. Once mechanical assembly is completed fully integrated testing of displacer actuation, piston position, generator speed control and measurement systems can be achieved.

Learning and memory mechanisms that are normally related to natural rewards, such as long-term potentiation (LTP) and depression (LTD), may be usurped by the voluntary intake of drugs of abuse. The maladaptive behaviour that characterizes addiction is thought to arise from persistent changes in excitatory synaptic function in brain reward circuits. The oval region of the dorsal bed nucleus of the stria terminalis (ovBST) is one such region susceptible to drug-induced synaptic remodeling and is implicated in drug-driven behaviors, reinforcement and stress-induced relapse to drug-seeking. Using whole-cell voltage clamp recordings of ovBST neurons in brain slices prepared from adult Long-Evans rats, we demonstrated an unrestrained increase in AMPAR-mediated excitatory transmission with maintenance of cocaine self-administration. This is unlike self-administration of a natural reward, in which we observed an enhancement and then decline of AMPAR-mediated transmission with continued intake. Additionally, we demonstrate impairment in NMDAR-mediated LTD in ovBST neurons with cocaine self-administration. This impairment may be due to resilient GluN2B-containing NMDARs, as application of a GluN2B-antagonist rescued impaired LTD. Based on models of NMDAR-mediated bidirectional plasticity we suggest that a drug-induced de-regulation between GluN2A and GluN2B subunits impairs LTD, which may underlie the enhancement AMPAR-mediated transmission. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-05-31 09:46:39.312

No abstract available. / Thesis (MBA)-University of Natal, 2002.

Following mineral-sand mining in the northern sandplains near Eneabba, southwestern Australia, rehabilitation managers have the difficult task of restoring shrubland communities of exceptional plant species richness. Management aims to restore a fully functional and self-sustaining shrubland community with similar vegetation and resilience properties to that of the surrounding natural vegetation. This thesis examines the performance of the restoration program by Iluka Resources Ltd. (and their predecessors) by comparing current vegetation properties and their response to fires on previously mined land versus the surrounding natural shrubland. As biomass accumulates post-restoration, fires will return as a natural disturbance factor and, as a result, a desirable measure of restoration success might include the ability of the postmined lands to recover from disturbance. Pre-burnt plant species diversity, composition, structure and key functional attributes in four mined sites rehabilitated 8 (R8) to 24 (R24) years ago were compared with those of surrounding natural areas classified on the basis of substrate type (low and high sand dunes, shallow sand swales, sand over laterite and sand over limestone). The rehabilitated sites (except R8) had more species (about 140) than natural sites (about 100) with 12–37% species in common with natural sites. Floristic composition was most similar to the local swales and dunes (physically closest). / Two strong colonizers, the fire-killed Acacia blakelyi and the fire-tolerant Melaleuca leuropoma, were universally present. Plant densities were about a quarter to half those of natural sites. Fire-resprouters were under-represented. Growth-form distributions were most similar to those of the dunes, with some woody shrubs up to 2.5 m tall present. Greater iron levels and soil hardness (penetrability) were the only soil factors consistently greater in rehabilitated sites. Following experimental fires at the same study sites, species richness fell by 22–41% in rehabilitated sites but increased by 4–29% in natural sites. Species present before fire were reduced by 40–56% in rehabilitated sites and 4–12% in natural sites. Only 42–66% of resprouting species recovered in rehabilitated sites, whereas 96–100% recovered in natural sites. Nonsprouting species recruitment was also lower in rehabilitated (18–57%) than natural (67–85%) sites. Seedling mortality over the first summer after fire was higher in rehabilitated sites (59-86% death of individuals) than in natural sites (14-60%). PCoA ordination showed that fire altered the floristic composition of rehabilitated sites much more than it did in natural sites, mostly attributable to the loss of the extant resprouter species. It was found that the smaller lignotuber size (source of dormant buds) recorded in rehabilitated (vs. natural) resprouters was responsible for their higher post-fire mortality. For equivalent crown size in ten common lignotuberous shrub species, lignotuber circumferences were, on average, 50% smaller at rehabilitated sites. / As a result, overall persistence in these species was much lower in rehabilitated (mean of 52% alive, range of 11–93%) versus natural sites (mean of 96%, range of 79–100%), but improved with time since restoration for five of the ten selected species. Apart from differences in the age of the plants (natural sites having much older plants recruited after previous fires), the lower soil penetrability at rehabilitated sites may have restricted lignotuber development. A tradeoff favoring a higher crown volume to lignotuber size ratio was also apparent in nine of the ten species with greater crown volumes (by 37%) and smaller lignotubers (by 36%) in rehabilitated sites. Demographic attributes for six selected woody species were compared between rehabilitated and natural sites (~3-30 years since disturbance) to investigate growth patterns and optimum fire-return intervals. At matched years since restoration or last fire, nonsprouter species in rehabilitated sites grew larger (1.1 to 4.7 times) and produced/stored more viable seeds per plant (1.1 to 10.9 times). Despite older aged individuals in natural sites at matched years since restoration vs. last fire, restored resprouters were larger (1.1 to 3.6 times) and produced/stored more viable seeds (1.1 to 6.9 times). Although greater growth and fecundity rates were recorded in rehabilitated sites, the estimated optimum fire-return interval based on maximum seed production was similar in rehabilitated and natural sites for five out of six species. / However, mean fire intervals typical of surrounding natural vegetation near the Eneabba area (13 years over the last 40 years) may not be suitable for rehabilitated minesites at Eneabba, whereby longer initial fire intervals (20–30 years) would better ensure persistence of resprouter individuals via the seedling recruitment strategy and resprouting strategy. Iv My study indicated that the returned vegetation can at present be classified as “rehabilitated” or “partially restored” but not “completely restored” since the original plant diversity, composition, structure, and resilience properties to fire have not yet been achieved. It may not be possible/realistic to achieve complete restoration since mining is such a destructive disturbance type that some complex ecological attributes may take centuries to develop. I discuss six key factors as important in improving the overall restoration success at Eneabba: 1) restoration of a deeper topsoil and looser subsoil profile; 2) collection of appropriate amounts of only local provenance species, mulch and topsoil; 3) control of highly competitive species; 4) management of fertilizer additions; 5) reseeding and replanting in subsequent years after the initial restoration treatments, including after initial fires; and 6) delaying the introduction of management fires until the restored vegetation develops sufficient fire-resilience properties.

Thesis (Ph.D.)--Erasmus Universiteit Rotterdam, 2004. / Title from title screen (viewed on January 11, 2006).

Business School, Diss.--Copenhagen, 2004. / Zsfassung in dän. Sprache.

Thesis (M.B.A.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 95-97).

Thesis (M.B.A.)--University of Hong Kong, 1994. / Includes bibliographical references.

Thesis (M.B.A.)--University of Hong Kong, 1998. / Includes bibliographical references.

Thesis (M.B.A.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 80-81).