Publication Search Results

Now showing 1 - 10 of 16

  • (2006) Botfield, Andrew
    In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 •/O2 •−, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 •/O2 •−). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by •OH (HCOO•/CO2 •− and 3HGA•2−). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that •OH and CO3 •− are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 •−, is suggested to be generated by the interaction of •OH and O2 •− with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 •− and the previously dismissed •OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).

  • (2006) Marshall, Lucy Amanda
    One challenge that faces hydrologists in water resources planning is to predict the catchment's response to a given rainfall. Estimation of parameter uncertainty (and model uncertainty) allows assessment of the risk in likely applications of hydrological models. Bayesian statistical inference, with computations carried out via Markov Chain Monte Carlo (MCMC) methods, offers an attractive approach to model specification, allowing for the combination of any pre-existing knowledge about individual models and their respective parameters with the available catchment data to assess both parameter and model uncertainty. This thesis develops and applies Bayesian statistical tools for parameter estimation, comparison of model performance and hierarchical model aggregation. The work presented has three main sections. The first area of research compares four MCMC algorithms for simplicity, ease of use, efficiency and speed of implementation in the context of conceptual rainfall-runoff modelling. Included is an adaptive Metropolis algorithm that has characteristics that are well suited to hydrological applications. The utility of the proposed adaptive algorithm is further expanded by the second area of research in which a probabilistic regime for comparing selected models is developed and applied. The final area of research introduces a methodology for hydrologic model aggregation that is flexible and dynamic. Rigidity in the model structure limits representation of the variability in the flow generation mechanism, which becomes a limitation when the flow processes are not clearly understood. The proposed Hierarchical Mixtures of Experts (HME) model architecture is designed to do away with this limitation by selecting individual models probabilistically based on predefined catchment indicators. In addition, the approach allows a more flexible specification of the model error to better assess the risk of likely outcomes based on the model simulations. Application of the approach to lumped and distributed rainfall runoff models for a variety of catchments shows that by assessing different catchment predictors the method can be a useful tool for prediction of catchment response.

  • (2006) Hewitson, Steve
    The availability of GPS signals is a major limitation for many existing and potential applications. Fortunately, with the development of Galileo by the European Commission (EC) and European Space Agency (ESA) and new funding for the restoration of the Russian GLONASS announced by the Russian Federation the future for satellite based positioning and navigation applications is extremely promising. This research primarily investigates the benefits of GNSS interoperability and GNSS/INS integration to Receiver Autonomous Integrity Monitoring (RAIM) from a geometrical perspective. In addition to these investigations, issues regarding multiple outlier detection and identification are examined and integrity procedures addressing these issues are proposed. Moreover, it has been shown how the same RAIM algorithms can be effectively applied to the various static and kinematic navigation architectures used in this research.

  • (2006) Swarna, Ravindra Babu
    The complementary advantages of GPS and INS have been the principle driving factor to integrate these two navigation systems as an integrated GPS/INS system in various architectural forms to provide robust positioning. Although the loosely coupled and tightly coupled GPS/INS systems have been in existence for over a decade or two and performed reasonably well, nevertheless, the tracking performance was still a concern in non-benign environments such as dynamic scenarios, indoor environments, urban areas, under foliages etc., where the GPS tracking loops lose lock due to the signals being weak, subjected to excessive dynamics or completely blocked. The motivation of this research, therefore, was to address these limitations with an integrated GPS/Pseudolite/INS system using ultra-tight integration architecture. The main research contributions are summarised as below: (a) The performance of the tracking loops in dynamic scenarios were analysed in detail with both conventional and ultra-tight software receivers. The stochastic modelling of the INS-derived Doppler is of utmost importantance in enhancing the benefits of ultra-tight integration, and therefore, two popular stochastic techniques Gauss Markov (GM) and Autoregressive (AR), were investigated to model the Doppler signal. The simulation results demonstrate that the AR method is capable of producing better accuracies and is more efficient. The algorithms to determine the AR parameters (order and coefficients) were also provided. (b) The various mathematical relationships that elicit the understanding of the ultra-tightly integrated system were derived in detail. The Kalman filter design and its implementation were also provided. Various simulation and real-time experiments were conducted to study the performance of the filter, and the results confirm the underlying assumptions in the theoretical analyses and the mathematical derivations. Covariance analysis was also performed to study the convergence and stability effects of the filter. (c) Interpolator design using signal processing techniques were proposed to increase the sampling rate of the INS-derived Doppler. To efficiently realise the interpolator transfer function, two optimal techniques were investigated Polyphase and Cascaded Integrator Comb (CIC), and our results show that CIC was more efficient than polyphase in accuracy and real-time implementations. (d) The integration of Pseudolites (PL) with INS in ultra-tight configuration was analysed for an indoor environment. The acquisition and tracking performances of Pseudolites-only and Pseudolite/INS modes were compared to study the impact of the inertial signals aiding. The results demonstrate that aiding of the inertial signals with the baseband loops (acquisition and tracking) improve the overall tracking performance. An overview on the effects of the pseudolite signal propagation is also given. (e) Simulation and real-time experiments have been conducted to evaluate the proposed algorithms and the overall design of the ultra-tightly integrated system. A comparison was also done between GPS/PL/INS and GPS/INS integrated systems to study the potential advantages of the pseudolite integration. The details of the field experiment are provided. The data from a real-time experiment was processed to further evaluate the robustness of the system. The results confirm that the developed mathematical models and algorithms are correct.

  • (2006) Stenekes, Nyree
    Urban water recycling has been promoted as one of several ways that water use efficiency could be improved in Australia s cities, but few such schemes have been introduced. Many urban water-recycling schemes have been proposed, but often, these projects have been rejected because of community opposition. These difficulties suggest that recycling water is not just about having the right answer to any problem, but about the way in which the question is addressed. It is concerned with how practice is institutionalised; not just the rule making, but also the understandings and values that make the rule-making possible. In this thesis, the question of how the system of water governance could be strengthened to encourage sustainable water use through water recycling is examined. An analysis of experiences in three Australian case studies is conducted, in which recycled water was proposed for sustainability, to illuminate the way in which water use is institutionalised. Particular attention is given to the construction of meaning in relation to water use, by considering how water problems are framed and negotiated by different stakeholders and groups and the significance of the multiplicity of interpretive frameworks in use for the institutionalisation of practice. The analysis draws on institutional organisational theory and interpretive methods, which regard interpretation as one element (cognitive) in the stabilisation of social practice and closely linked to organisation (regulative) and values (normative). The study findings suggest meaning was a very important part of institutional change. Participants tended to construct policy issues as they became involved by drawing on different interpretive frameworks embodying different values and expectations. These interpretations reflected the organisational structuring of practice, such that the position/role in the organisational field reflected an actor s interpretation of problems and/or solutions. Outcomes of the study suggest that institutionalising change in water management is problematic and depends on changes in the regulative, normative and cognitive dimensions of practice, as part of a continuous feedback loop between interpretation and practice. This view of change contrasts with existing research, which tends to see the problem in terms of influencing attitudes of specific groups and assumes preferences precede the action.

  • (2006) Kwonpongsagoon, Suphaphat
    Extraction, production, utilization and disposal of material resources have been undertaken continuously for much of human histories. Unavoidably, all of these activities have disturbed our environment, and subsequently have been harmful to humans and ecosystems in this and future generations. Due to time lag associated with both environment impact and the effects of measures taken to reduce this impact, existing approaches (i.e. monitoring and reacting) do not give sufficiently rapid feedback for effective environmental management. With regard to the complexity and concern related to environment-health chain effects, there is currently no environmental tool or approach that can provide comprehensive information and indicators covering all major environment and health themes, to enable decision makers to make informed judgements about regional policies and plans, relating to the sustainable use and disposal of material resources. Consequently, there is a need for developing a new approach by taking account of a multidisciplinary concept used in this thesis. Substance Flow Analysis (SFA) has been mainly applied in order to provide input information for Health Risk Assessment (HRA). The SFA approach provides the quantity of the substance that is transported (flows) and stored in the system (stock), and of which sub-system, flow, and process is the greatest concern. The HRA approach provides estimates of human health risk associated with site, activity and facility. An environmental fate and transport model is another key knowledge area incorporated into the HRA process. An integrating method of SFA, environmental fate and transport, and HRA is developed and illustrated by a case study of cadmium in Australia. This thesis shows that this new integration of existing stand-alone methods can provide holistic information and useful indicators covering all significant economic activities, environment, flows, and health risk assessment for selected substances. This enables better decision making on the use and disposal of substances at a range of levels in the economy, from corporations to regions and nations.

  • (2006) Tajziehchi, Mojtaba
    Two dimensional experimental and numerical modeling of wave transmission and wave-induced current over detached submerged breakwaters has been carried out in this thesis. Two preliminary 3D and a comprehensive series of 2D laboratory experiments have been conducted in the wave basin and 3 m wide wave flume. The preliminary 3D experimental tests qualitatively investigated the flow behavior behind a submerged breakwater and confirmed the validity of the 2D tests. The 2D laboratory tests examined wave breaking, reflection, transmission as well as wave-induced set-up and currents over submerged breakwater/reef structures. Different approaches to experimental data processing are examined in producing reliable application of the 2D laboratory measurements. Sensitivity of wave transmission coefficient, wave-induced set-up and wave-induced discharge over submerged breakwaters to other dimensional and non-dimensional parameters are comprehensively investigated. Previously published analytical/experimental studies for predicting/calculating wave breaking, wave transmission, wave-induced set-up and current are discussed and compared with the present experimental results. Improved equations/models are presented. Numerical modeling of the hydrodynamic effects of wave breaking and flow over a submerged breakwater is investigated using Delft3D. The capability of the Delft3D numerical model to simulate wave height transformation and wave-induced current over submerged breakwaters is provided. Four different approaches using combinations/options within the two main modules of Delft3D (SWAN and FLOW) are tested in the numerical simulations and the results are compared to the laboratory experimental data. Guidance is provided as to the most appropriate application of WAVE/FLOW/ROLLER modules in Delft3D for the reliable prediction of discharge and wave height over different width submerged breakwaters.

  • (2006) Lim, Seok San
    The erosion behaviour of clay soils has been investigated through a comprehensive program of laboratory testing. Three different erosion test methods have been employed including the rotating cylinder test (RCT), the hole erosion test (HET), and the slaking test (SLT). A new rotating cylinder test device is designed and manufactured capable of testing disturbed and undisturbed soil samples in saturated and unsaturated states. Details of the equipment along with its calibration, testing and sampling procedures are provided. The HET has been reviewed and modified to provide consistent test results. In addition, the slaking test has been customised to accept samples identical to those used in the RCT. A total 111 RCT, 139 HET, and 108 slaking tests have been conducted and analysed. Typical shapes of the erosion curves are identified, based on a wide range of shear stresses and erosion rates analysed. Correlations are presented between the RCT and HET, and between the RCT and SLT to allow characterisation of clay soil erosion in a consistent and unified manner. The erosion modes of clay soils are investigated and categorised into three main groups: dispersive erosion , saturated non-dispersive erosion , and unsaturated non-dispersive erosion . It is shown that soils falling in the same category exhibit near identical erosion characteristics. Factors affecting clay soil erodibility are investigated and displayed for each erosion mode. All findings are presented in a unified framework. A suggested procedure is provided for the evaluation erosion potential in clay soils for practical applications.