89,593 results

  • Betaine analogues and related compounds for biomedical applications

    Vasudevamurthy, Madhusudan (2006)

    Doctoral thesis
    University of Canterbury Library

    Living cells accumulate compensatory solutes for protection against the harmful effects of extreme environmental conditions such as high salinity, temperature and desiccation. Even at high concentrations these solutes do not disrupt the normal cellular functions and at times counteract by stabilizing the cellular components. These properties of compensatory solutes have been exploited for stabilizing proteins and cells in vitro. Betaines are widespread natural compensatory solutes that have also been used in other applications such as therapeutic agents and polymerase chain reaction (PCR) enhancers. Some biomedical applications of novel synthetic analogues of natural betaines were investigated. Natural compensatory solutes are either dipolar zwitterionic compounds or polyhydroxyl compounds, and the physical basis of compensation may differ between these, so one focus was on synthetic betaines with hydroxyl substituents. The majority of the synthetic solutes stabilized different model proteins against stress factors such as high and low temperatures. The presence of hydroxyl groups improved protection against desiccation. The observed stabilization effect is not just on the catalytic activity of the enzyme, but also on its structural conformation. Synthetic compensatory solutes have a potential application as protein stabilizers. Dimethylthetin was evaluated as a therapeutic agent and found to be harmful in a sheep model. However, from the study we were able to generate a large-animal continuous ambulatory peritoneal dialysis (CAPD) model and showed that glycine betaine could be added to the dialysis fluid in chronic renal failure. Some synthetic compensatory solutes reduce the melting temperatures of DNA better than most natural solutes. Synthetic solutes were identified that have potential to enhance PCR and could replace some reagents marketed by commercial suppliers. Density, viscosity and molecular model data on the solutes showed correlations with the biochemical effects of the solutes, but no physical measurements were found that reliably predicted their potential for biotechnological applications.

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  • Efficient Kiln Drying of Quality Softwood Timber

    McCurdy, Murray Charles (2006)

    Doctoral thesis
    University of Canterbury Library

    This thesis is a study of the kiln drying of radiata pine with a primary focus on the change in wood colour that occurs during this process. The energy efficiency of the drying process has also been examined using computer modelling. The aim of this work was to develop guidelines for commercial wood dryers who wish to produce high quality appearance grade timber in a competitive commercial environment. The colour change in radiata pine wood during kiln drying is mainly caused by sap compounds accumulating at the wood surface and reacting to form coloured compounds. The initial research involved drying experiments designed to determine the relationship between this colour change and the kiln schedule and also measure the accumulation of colour forming compounds. The kinetics of the colour change reaction were also measured using two methods, one in-vitro and the other using small samples of wood. From these experiments a colour change equation was developed that predicts the rate of colour formation based on the drying conditions and this was incorporated into a kiln stack model along with an energy efficiency model. The combined model was used to simulate the drying process to find schedules optimised for energy use and wood quality. The model was also used to simulate the energy efficiency of different humidity control configurations for wood drying kilns. A kiln micro-sensor system was also developed for use in kiln diagnostics and control with the particular aim of identifying areas in wood drying kilns with adverse drying conditions. The recommendation to kiln operators wishing to reduce colour change is to not exceed 70? and to use lower relative humidity schedules with a wet bulb depression of 15-20?. Operating at lower humidity can increase the energy used by the kiln so it is also recommended that kiln designers incorporate heat recovery into the humidity control mechanisms of the kiln.

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  • A Study on Laser Forming Processes with Finite Element Analysis

    Jung, Hyung Chul (2006)

    Doctoral thesis
    University of Canterbury Library

    Laser forming is an innovative technique that uses a defocused laser beam to form sheet metal by thermal stresses rather than external forces. Promising potential applications of laser forming include rapid prototyping, straightening, aligning and adjusting of macro/micro-metallic components. Research to-date on laser forming has been largely focused, theoretically and experimentally, on the problem of characterization of process parameters on the forming results, and computational simulations of laser forming remain limited only providing the insight into the process. This study investigates the laser forming processes using the finite element analysis with respect to material responses during the processes, including complex processes, process optimization, process reliability and the effects of thermal and mechanical material properties. The first part of this thesis describes a nonlinear transient three-dimensional heat transfer finite element model and a rate dependent three-dimensional deformation model, which are developed for the laser forming simulations. Simulations are performed using an indirect coupled thermal-structural method for the processes of a straight-line heating, a circle-line heating, and a laser micro-adjustment. The thermo-mechanical behaviours during the straight-line heating process are presented in terms of temperature, stress and strain, and displacement distributions. The emphasis in the circle-line heating simulations is placed on the characterization of the quality of the deformed geometry by obtaining the radial and circumferential waviness. The micron size movements induced by laser point heating are focused the simulations of the micro-adjustment process. Simulation results are validated by comparison with published data or correlation to engineering point of view. The second part of this thesis presents the development of an effective method to determine optimum process parameters in laser forming. For the process optimization, design optimisation techniques are introduced into the finite element analysis of the laser forming process. The optimum parameter values to produce a predefined bend angle of 3° in the straight-line heating process are sought by two optimization procedures - one is the procedure involving the non-gradient method and the other is the gradient-based method. Optimum values of laser power, feed rate, beam diameter and number of passes are determined to produce a predefined bend angle in a multiple straight-line heating process using the two optimization procedures. A more suitable optimisation method for laser forming is chosen, which is used for a new optimisation problem to generate a maximum bend angle in a single pass of laser forming. In the third part of this thesis, a strategy to assess the reliability of the laser forming process is established by employing a well-known reliability analysis method, the Monte Carlo simulation. Robustness of the straight-line heating process of producing 3° with the optimum parameters determined by process optimization is evaluated with regard to the uncertain input variables of laser power, feed rate, plate thickness and coefficient of thermal expansion via the Monte Carlo simulations based on the finite element simulations of the process. The final part of this thesis identifies the effects of material properties on the bend angle resulting from laser forming. Process sensitivity to the properties of coefficient of thermal expansion, thermal conductivity, specific heat capacity and elastic modulus is investigated by measuring the Pearson product-moment correlation coefficient between the properties and the bend angle, which are based on the Monte Carlo simulations of laser forming. The conclusion is that the developed finite element models contribute to a better understanding of the laser forming process, and the optimization procedure is able to be used for straightening, aligning and adjusting of components.

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  • Modelling the germination of Buddleia Davidii under constant conditions with the hydrothermal time concept

    Jay, Julien P.A. (2006)

    Masters thesis
    University of Canterbury Library

    Buddleia davidii is a weed naturalized in New Zealand. It invades radiata pine plantations and causes major growth reduction and economic losses. Modelling its germination for predicting its occurrence will help foresters minimise its influence in forest plantations. Germination experiments have been carried out in laboratory to assess the influence of seed origin, defoliation, temperature and water stress on germination. Defoliation treatments did not significantly affect germination. The pattern of germination for seeds from four different places within New Zealand revealed so little difference that there is no need to define different models according to the site considered. However this similarity in germination pattern is limited to New Zealand and cannot be generalised to other countries where germination appears to be significantly different. The germination of Buddleia davidii seed appeared to be a function of hydrothermal time. The base, optimum and ceiling temperatures for Buddleia are respectively 9, 25 and from 30 to 35?, and Buddleia seed germinate between 0 and approximately -6 bars. In constant conditions, the predicted germination for Buddleia davidii with the thermal time model was limited to sub-optimal temperatures and the hydrotime and hydrothermal time models described well the germination pattern at any temperature and water potential. The modified hydrothermal time model proposed by Alvarado and Bradford (2002) most accurately predicted germination although it tended to overestimate the asymptotes. Overall the hydrothermal time model allowed prediction of actual timing of germination with much accuracy. This threshold model can therefore be used for modelling the germination of Buddleia davidii subjected to constant temperature and water potential conditions.

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  • Formulation & Calibration of a Numerical model of the tidal hydraulics of McCormacks Bay

    Flanagan, James P A (1997)

    Masters thesis
    University of Canterbury Library

    The experimental investigation in this report was conducted both as indicator of the problems in McCormacks bay, and also as a base for the calibration of a numerical model of the hydraulic characteristics of the bay. There are some issues of public concern associated with the bay at the present time. These are related to dominant algae populations and their related problems, and the desire to preserve the existing bay as a healthy marine environment. Numerical models can be a useful tool to test various management options. A component of this study involved the calibration of a numerical model which described the response of the bay to tidal functions in the estuary. Calibration was achieved using data from measurements taken on the eighteenth of December 1996. The model was based specifically around the main central culvert running under the causeway. The model showed that an increase in the depth of this culvert would increase the range of water levels in the bay by up to 23%. This is significant and would increase the tidal exchange in the bay, thereby promoting circulation.

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  • Hybrid forest modelling of Pinus Radiata D. Don in Canterbury, New Zealand

    Pinjuv, Guy L (2006)

    Doctoral thesis
    University of Canterbury Library

    During this study two models were developed to predict growth of Pinus radiata D.Don plantations in Canterbury, New Zealand. The first, CanSPBL(1.2), is a model for whole rotations of stands owned by Selwyn Plantation Limited in Canterbury. The second model, CanSPBL(water) is a hybrid growth model for the Selwyn estate in Canterbury that incorporates an index of root zone water balance over the simulation period. An existing stand growth and yield model CanSPBL was examined using a validation dataset of PSP measurements that were not used in model fitting. Projection bias was shown for mean top height, basal area per hectare, and residual stand stocking particularly for stands at elevations exceeding 450 metres. The new model, CanSPBL(1.2) showed an increase in precision of 4 - 46% over CanSPBL(1.0) at a stand level. The components of the stand model include mean top height, basal area per hectare, stems per hectare, and diameter distribution. The mortality model was made in conjunction with managers at CanSPBL to exclude catastrophic mortality events from model projections. Data used for model fitting was filtered using a mortality index based on the -3/2 power law. An examination of this model with an independent dataset showed little apparent bias. The new model, CanSPBL(water) was developed to include an index of water balance over the simulation period. Water balance estimates were made using a sub model for root zone water balance included in the hybrid physiological model 3-PG (Landsberg and Waring, 1997). The new model showed an increase in precision of 1 - 4% over CanSPBL(1.2) at a stand level (with the exception of the model for maximum diameter which showed a decrease in precision of 0.78%) using climatic inputs that included yearly variation. However the model showed increases of precision from 0.5 to 8% (with the exception of maximum diameter again, showing a decrease in precision of 0.13%) using long term monthly average climatic inputs. The components of the stand model also include mean top height, basal area per hectare, stems per hectare, and diameter distribution. The mortality model was also fitted with a data set filtered using a mortality severity index based on the -3/2 power law to exclude catastrophic mortality events. An examination of this model with an independent dataset showed little apparent bias. Two models to predict a one sided canopy leaf area index (LAI) of radiata pine stands in the Canterbury Plains of New Zealand were also developed. The models were fitted using non-linear least squares regression of LAI estimates against stem measurements and stand characteristics. LAI estimates were derived from digital analysis of fisheye lens photography. The models were kept simple to avoid computational circularity for physiological modelling applications. This study included an objective comparison and validation of a range of model types. The models CANTY (Goulding, 1995), CanSPBL(1.2) (Pinjuv, 2005), CanSPBL-water (Pinjuv, 2005), and 3-PG (Landsberg and Waring, 1997) were compared and validated with the main criteria for comparison being each model s ability to match actual historical measurements of forest growth in an independent data set. Overall, the models CanSPBL(water), and CanSPBL(1.2) performed the best in terms of basal area and mean top height prediction. Both models CanSPBL(water), and CanSPBL(1.2) showed a slightly worse fit in predictions of stocking than did the model CANTY. The hybrid model 3PG showed a better fit for the prediction of basal area than the statistically based model CANTY, but showed a worse fit for the prediction of final stocking than all other models. In terms of distribution of residuals, CanSPBL(1.2) had overall the lowest skewness, kurtosis, and all model parameters tested significant for normality. 3PG performed the worst on average, in terms of the distribution of residuals, and all models tested positively for the normality of residual distribution.

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  • FACTS device modelling in the harmonic domain

    Collins, Christopher Donald (2006)

    Doctoral thesis
    University of Canterbury Library

    This thesis describes a novel harmonic domain approach for assessing the steady state performance of Flexible AC Transmission System (FACTS) devices. Existing harmonic analysis techniques are reviewed and used as the basis for a novel iterative harmonic domain model for PWM FACTS devices. The unified Newton formulation adopted uses a combination of positive frequency real valued harmonic and three-phase fundamental frequency power-flow mismatches to characterise a PWM converter system. A dc side mismatch formulation is employed in order to reduce the solution size, something only possible because of the hard switched nature of PWM converters. This computationally efficient formulation permits the study of generalised systems containing multiple FACTS devices. This modular PWM converter block is applied to series, shunt and multi-converter FACTS topologies, with a variety of basic control schemes. Using a three-phase power-flow initialisation and a fixed harmonic Jacobian provides robust convergence to a solution consistent with time domain simulation. By including the power-flow variables in the full harmonic solution the model avoids unnecessary assumptions regarding a fixed (or linearised) operating point, fully modelling system imbalance and the associated non-characteristic harmonics. The capability of the proposed technique is illustrated by considering a range of harmonic interaction mechanisms, both within and between FACTS devices. In particular, the impact of transmission network modelling and operating point variation is investigated with reference to ac and dc side harmonic interaction. The minor role harmonic distortion and over-modulation play in the PWM switching process is finally considered with reference to the associated reduction in system linearity.

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  • Engineering Geology and Geotechnical Investigation of Highwall Stability at the Proposed Terrace Opencast Coal Mine, Reddale Valley, Reefton.

    Lea, Joanna Mary (2006)

    Masters thesis
    University of Canterbury Library

    This thesis presents an engineering geological and geotechnical investigation of the proposed Terrace Opencast Coalmine highwall in the Reddale Valley, Reefton. The proposed pit will target the 4-11m thick No. 4 Seam coal, which exists on the Valley floor beneath outwash gravels and Brunner Coal Measures (BCM) overburden dipping at 15-30° to the northwest. Rock coatings are providing friable sandstone units with protection from weathering in existing cut faces and may contribute to short term pit wall stability. The BCM core was divided into four geotechnical units for rock material testing purposes: unit 1 siltstone, unit 2 carbonaceous mudstone, unit 3 interbedded sandstone and carbonaceous mudstone and unit 4 loose sandstone. The average results for units 1-3 gave classifications within the medium to high porosity (9-13%) and dry density (2250-2470kg/m³) ranges, and medium to medium high slake-durability Id2 values (72-94% retained). Unit 4 (loose sandstone) recorded very low dry density (1694 kg/m³) and slake-durability Id2 (9%) average values. Strength testing confirmed that the units can be classed as weak rocks, with average UCS values of 12.8-13.7MPa for units 1-3, and for all four units Is(50) from point load testing of 0.26-0.62MPa with low cohesion values (0-6.2MPa) from triaxial testing. Friction angles from triaxial tests gave high values of 32-45°, while direct shear tests established 15° internal friction for bedding planes in carbonaceous mudstone and 37° for a high angle defect in interbedded sandstone/carbonaceous mudstone. The average Young's modulus values ranged from 0.82 to 10GPa, and Poisson's ratio between 0.39 and 0.50. Eight scanline defect surveys established that the major discontinuities in existing cut faces consist of high angle tension joints, shallow dipping bedding, and faults related to regional uplift. The defect orientations from the scanlines located in the southwest were significantly different from those in the northeast, and may be due to the faults that cross the Valley. In general the majority of defects displayed low persistence (less than 3m), were clean and tight, and had low joint roughness coefficients (JRC less than 6). Joint wall compressive strengths gave an average of 32MPa, but were affected by case-hardening on weathered faces. The results from the 8 drill holes analysed show that 37% of core was within the excellent rock quality designation class (RQD = 90-100%), while 29% was in the very poor quality rock (RQD = 0-25%). A semi-confined aquifer in the outwash gravels that will drain into the proposed pit was found to have a transmissivity of 58m²/day and hydraulic conductivity of 3.1 x 10⁻⁵ m/s. Kinematic feasibility assessment determined an optimum highwall orientation of 65° dip to 120° (dip direction), which is within at least 20° of the coal seam strike. The likelihood of planar, wedge or toppling failure depends on whether the structural conditions are similar to those encountered in the southwest or northeast scanlines, as well as the persistence of the defects present. The occurrence of small scale (less than 1m offset) 'step-up' normal faults, and the three larger faults that cross the valley, all of which are related to regional uplift, will also affect which failure mode will be kinematically feasible. Other crucial slope stability considerations include groundwater inflow from the saturated overburden and bedding parallel failures on the footwall dip slope of the pit. An investigation into case hardening on existing cut faces identified three interconnected rock coatings: iron films, lithobiontic (biological) and clay-dominated crusts. Jarosite was found at sites with abundant pyrite and the oxidation of iron may have been aided by microbial activity. A green algae inhabiting pore spaces approximately 1mm below the surface was noted beneath an iron film and it is suggested to be similar to that found in arid environments. Although lithobiontic and clay-dominated crusts did not provide the weathered surface with any additional strength, they were observed to form relatively quickly (from months to less than 5 years) and will aid short term stability by providing the batters with protection from weathering processes. This project concluded that the overburden material in the proposed highwall can be expected to behave like weak rock and in some cases (such as the loose sandstone) can be expected to have soil characteristics. Highwall stability is more likely to be affected by substantial inflows of groundwater than highly persistent joint sets. Establishment of the highwalls in their final position in the early mining stages will enable development of rock coatings that are expected to aid short and long term stability.

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  • Design of a 3 axis wear testing device to evaluate the effect of slide to roll ratio on ultra high molecular weight polyethylene wear in total knee replacements

    Low, Benjamin (2005)

    Masters thesis
    University of Canterbury Library

    Multidirectional motion occurs in total knee replacements (TKR), is a major factor in ultra high molecular weight polyethylene (UHMWPE) wear and is a requirement for wear tester and simulators. There are three ways the femoral component can move relative to the tibial component; sliding, rolling and gliding and these are defined by the slide to roll ratio. Previous wear tester research has investigated the effects of multidirectional motion and slide to roll ratio, individually but not combined. The project aim was to design a machine that combined multidirectional motion with variable slide to roll ratio. A three station wear testing machine was designed and built featuring flexion extension, variable anterior posterior translation, variable internal external rotation and a 2KN load per station. The TKR was simplified to a cylinder on flat. Lubrication was 25% bovine serum and each station had its own recirculation system. A million cycle validation test was successfully carried out on non-irradiated UHMWPE samples using a slide to roll ratio of 1 : 0.5 and the mean wear rate was 14.7mg/10^6 cycles. Polished areas and scratches from 3rd body abrasion were observed. Magnification revealed a fine ripple pattern with a 1-2 micron periodicity. Ripples were randomly oriented, perpendicular to the primary direction of motion and a small number were running parallel to the primary direction of motion, indicative of rolling motion. The results from the validation study show that the knee joint wear tester is capable of producing wear rates and wear mechanisms similar to those observed in other wear testers and knee joint simulators and has met the aim of the project.

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  • Estimating regional supply and delivered cost of forest and wood processing biomass available for bioenergy

    Robertson, Kimberly Ann (2006)

    Masters thesis
    University of Canterbury Library

    New Zealand has ratified the Kyoto Protocol and agreed to reduce greenhouse gas emissions to 1990 levels in the first commitment period 2008-2012. Energy generated from renewable sources, such as New Zealand plantation forests and wood processing sites, is considered greenhouse gas neutral. But the use of biomass for bioenergy in New Zealand is very small. Some of the reasons for this include a lack of information about the future fuel supply and delivered cost. This thesis aims to provide a methodology to estimate biomass fuel availability and the delivered cost, of a range of forest and wood processing sources within a district, and to analyse the impact of harvest age, harvesting practices, terrain, collection and chipping costs, opportunity cost and transport costs on the availability and delivered cost of biomass for bioenergy. The six biomass streams included were chiplogs, forest landing residues, cutover residues, sawdust, bark and chip. The methodology was developed based on an area in Canterbury, and tested on an area in the Nelson/Marlborough region. It utilises forest growth models, Geographic Information Systems and Microsoft Excel. Growth models allow the analysis to be customised to a particular area or region, while the use of GIS allows the model to take spatial aspects (for example slope and transport distance) into consideration. Developing the overall framework within Excel allows easy analysis of the results and changes to the underlying assumptions. Opportunity costs make up a large proportion of the total cost of delivery for the chiplog, sawdust, bark and chip biomass and need to be included in any estimate of cost for these biomass streams. The logistic system chosen for collecting and chipping the forest residues has a large impact on their delivered cost as do the transport costs. However transport cost is not the most significant influence on the delivered cost of other biomass streams. The use of biomass for electricity generation only is not currently economic in either of the areas analysed. The use of biomass for heat production is currently economic if compared to the electricity purchase price.

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  • Developing best practice in environmental impact assessment using risk management ideas, concepts and principles

    Fietje, Leo (2001)

    Masters thesis
    University of Canterbury Library

    This thesis argues that the management of environmental impacts has many analogies with the management of risk and practice can be improved by using ideas, concepts and principles found in the management of risk in other spheres of human activity. An overview of the challenges faced by environmental impact practitioners in New Zealand and reinforcement of its importance to the sustainable management of natural and physical resources under New Zealand's Resource Management Act is provided. Key risk management ideas, concepts and principles drawn from a variety of sources are listed and parallels drawn between these and existing environmental impact assessment practice in New Zealand. From this list a number are selected and opportunities for improving environmental impact assessment practice are explored. A number of opportunities are identified, starting with the need for a common language and methodology amongst practitioners. Categorisation of impacts to assist transparency of analysis and expression using frequency-consequence curves to aid and promote consistency of decision-making are further areas of opportunity. Risk management has several well-developed techniques for dealing with uncertainty and selection of assessment endpoints. The connection between communication of risk and public perception is an area with significant potential for communication about environmental impacts. Challenges with effective public participation in environmental decision-making are backgrounded and risk management practised in two high profile areas examined for opportunity for improved practice. Neither appears to offer opportunity for improvement in key decision-making areas. A relatively new indicator approach towards risk assessment called "healthy systems method" appears to have significant potential for cost-effective analysis of systems of various types and at various levels. This thesis identifies a number of other areas of risk management requiring further research to determine potential for achieving better practice in environmental impact assessment.

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  • Harmonic State Estimation and Transient State Estimation

    Yu, Kan Chi Kent (2006)

    Doctoral thesis
    University of Canterbury Library

    This thesis describes the algorithms and techniques developed for harmonic state estimation and transient state estimation, which can be used to identify the location of disturbance sources in an electrical power system. The previous harmonic state estimation algorithm is extended to include the estimation of time-varying harmonics using an adaptive Kalman filter. The proposed method utilises two covariance noise models to overcome the divergence problem in traditional Kalman filters. Moreover, it does not require an optimal covariance noise matrix of the Kalman filter to be used. The common problems faced in harmonic state estimation applications due to the influence of measurement bad data associated with measurements and the lack of measurement points, hence the system being partially observable, are investigated with reference to the Lower South Island of the New Zealand system. The state estimation technique is also extended to transient state estimation. Two formulation methods are outlined and the development of the proposed methodology is presented. Fault scenarios with reference to the Lower South Island of the New Zealand system are simulated to demonstrate the ability of transient state estimation in estimating the voltages and currents of the unmeasured locations, and applying the estimated results to search for the fault location. The estimation results are compared with PSCAD/EMTDC simulations to justify their accuracy.

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  • Guidelines for the Design of Augmented Reality Strategy Games

    Nilsen, Trond (2006)

    Masters thesis
    University of Canterbury Library

    With augmented reality, we can create interfaces that merge virtual objects and data seamlessly with the real world, potentially improving collaboration and interaction. This technology offers opportunities for games, allowing new designs that merge the diverse social and physical interaction of real world games with rapid interactivity and computing power of digital games. To date, research has primarily focused on issues of technology, interaction design, and nfrastructure; the design of compelling play has received little attention. We play games because they are enjoyable; therefore, in order to create attractive games, we must understand enjoyment. In games, engagement, social interaction, and emotional involvement are among the most common causes. We can design for engagement in play using Csikszentmihalyi's model of 'flow'; for social play by making communication easy, natural, and useful; and emotional involvement by understanding the mechanisms by which games stimulate us. Alongside an understanding of enjoyment, lessons must be drawn from design experience. AR Tankwar is an augmented reality strategy game developed over the course of this thesis, and has been evaluated in the field at a large games convention, and in a detailed comparative study with existing games on tabletop and desktop PC. Evaluations revealed predictable limitations with the technology, but also provided insight into how designers can make best use of the medium. Based on these activities, and existing knowledge of interaction and collaboration in augmented reality, this thesis addresses compelling play in augmented reality by developing a set of design guidelines for augmented reality games, with particular focus on strategy games.

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  • Neotectonics, Seismic and Tsunami Hazards, Viti Levu, Fiji.

    Rahiman, Tariq Iqbal Hamid (2006)

    Doctoral thesis
    University of Canterbury Library

    Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform - a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the southwest Pacific. The southeast coast of Viti Levu is a highly developed and populated part of Fiji and is vulnerable to the effects of large earthquakes that are expected to occur both onshore and offshore. The structural framework and the origin of seismicity within the Fiji Platform, as well as the seismic and tsunami hazards of central and southeast Viti Levu are investigated. The upper crust of southeast Viti Levu is dissected by several intersecting fault/lineament zones. These are mapped from remote sensing imagery of the surface (topography, radar, and aerial photos) and of the basement (magnetic), and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineament zones extend beyond the coastline to the offshore area of southeast Viti Levu. Here high resolution SeaBAT 8160 multibeam bathymetry data and seismic reflection data show that the fault zones occur along, and exert control on the locations of a number of linear submarine canyons. The morpho-structural expression of these canyons are contiguous with fault controlled physiographic features mapped on the nearshore marginal shelf (rectilinear bays and peninsulas, reef passages) and on land (fault valleys, slope and drainage alignments forming lineaments). The canyons are considered to have developed from several cycles of downslope incising and infilling events, whilst their positions were still primarily controlled by zones of weakness created by the fault zones. The principal fault sets in southeast Viti Levu represent generations of regional tectonic faulting that pervaded the Fiji Platform during and after disruption of the proto Fijian arc in the Middle to Late Miocene. These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2 to 30 km. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (M4) may result from complex rupture propagation through several linking fault segments of the mesh that lie close to optimum stress orientations. This interpreted model of distributed deformation through the fault mesh for southeast Viti Levu is inferred to be characteristic of the style of active deformation that occurs throughout the entire Fiji Platform. Seismic activity is primarily responsible for triggering submarine landslides that occur on the southeastern slope of Viti Levu. These slides typically occur on the outer barrier reef edge, as well as in submarine canyon heads and walls, and in the mid slope areas. They are characteristically translational and lack bathymetric evidence for displaced masses. Morphometric analysis and empirical modelling, show that slides triggered at shallow water depths, within 5 km of the coastline, at the outer barrier reef edge and submarine canyon heads, produce the largest near-field tsunami amplitudes. Such slides are interpreted to represent a significant local tsunami hazard. A detailed case study of the destructive 1953 Suva tsunami that followed the Ms 6.75 Suva earthquake, reveals that the source of this tsunami was a 60 million cubic metre submarine landslide at the head of the Suva Canyon, 4 km to the WSW of Suva City. A test simulation of this tsunami using the Geowave tsunami generation, propagation and inundation model, closely replicates the wave heights and arrival times recorded in 1953. This simulation also reveals that high variability in tsunami impact over short coastal distances of southeast Viti Levu is attributable to the complex interplay of wave propagation with the barrier reef system, erratic lagoon bathymetry and the irregularly shaped coastline. A predictive simulation using Geowave, based on an incipient failure in the 1953 source area and on a potentially worse case scenario event at or near high-tide, is used to show a maximum vertical run up of at least 4 m and a maximum horizontal inundation level of at least 400 m at the Suva coast. The seismic hazard of five sites on Viti Levu, including Suva City, Navua and Nausori Towns, and the Monsavu and Nadarivatu dam sites, is evaluated using a deterministic approach, and seven newly identified crustal fault earthquake source structures. The maximum magnitudes interpreted for these structures, estimated using empirical relationships, range from Mw 6.8 to 7.6. The Suva Canyon Fault, the Naqara Fault, the Mavuvu/Fault Lineament Zone and the Nasivi Fault provide the controlling maximum credible earthquakes (CMCE) at all the five sites. The CMCE peak ground acceleration values for Suva City range from 0.4g to 0.6g, for Nausori Town from 0.18g to 0.2g, for Navua Town from 0.27g to 0.32g, for Monasavu from 0.39g to 0.42g, and for Nadarivatu from 0.23g to 0.33g. The horizontal spectral accelerations at a period equal to 0.2 seconds, calculated using the CMCEs, are comparable to accelerations derived by probabilistic methods that have return periods between 50 and over 1000 years.

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  • An evaluation system for intelligent smart badges

    Liu, Yi (2006)

    Masters thesis
    University of Canterbury Library

    In this thesis we develop and test a software algorithm for an electronic smart badge system. The smart badge system we have developed has the ability to figure out the interests of people who wear the badge by using time and position information collected by the badge. The badge can also present feedback to the wearer, so that users may be guided to people will similar interests and so may have more effective conversations. The smart badge system is based on an inference system which uses a Bayesian network. Evaluation of the system was challenging because there were no completed badges that could be used. To overcome this, we developed a simulation of crowd behaviour in a conference setting. We tuned the parameters of the model using several test situations and the final simulated behavior appeared realistic. Compared to other smart badge systems, our work is unique because it is able to enhance conversation by the real time inference of common ideas or interests of the conversion participants.

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  • Novel Adaptive Equalization Techniques for a Transmit Diversity Scheme

    Zeng, Yan (2006)

    Masters thesis
    University of Canterbury Library

    Space-time block coding (STBC) has added a new dimension to broadband wireless communication systems. Applications such as wireless Internet access and multimedia require the transmission of high data rates over frequency selective fading channels. The reliability of the wireless communication system can be increased by using diversity techniques combined with an equalizer at the receiver to eliminate the inter-symbol interference caused by multipath propagation. Generalizing Alamouti's famous STBC method to frequency selective channels, Time Reversal-Space Time Block Coding (TR-STBC) was first introduced in [1] and has since been shown to be an effective transmit diversity scheme [2, 3, 4]. TR-STBC-based schemes are considered promising candidates for indoor transmission [5] as well as for the enhanced data rates of the global evolution (EDGE) system [2, 3]. The optimal equalizer for a TR-STBC-based transceiver is the Maximum Likelihood Sequence Estimator (MSLE), realized using the Viterbi algorithm. Unfortunately, a Viterbi equalizer is difficult to implement in real-time due its exponential increase in complexity with the number of antennas and the length of the channel impulse response. Thus, we consider an adaptive algorithm-based Decision Feedback Equalizer (DFE). Such a DFE requires only linear processing complexity while maintaining good performance. Theoretically, the two output streams of a 2 x 1 TR-STBC decoder are uncoupled in terms of the input signal statistics and uncorrelated in terms of the channel noise statistics. The standard approach to removing the inter-symbol interference from these streams is to use either two parallel independently-adapted Single-Input Single-Output (SISO) equalizers or to use a single Multiple-Input Multiple-Output (MIMO) equalizer. By exploiting the common second-order statistics of the two output streams, we proposea novel hybrid equalizer structure which shares the statistical information between two SISO equalizers while constraining them to have common tap weights. To accommodate various levels of performance versus computational complexity, we propose novel Least Mean Square (LMS), Normalized Least Mean Square (NLMS), and Recursive Least Squares (RLS)-based adaptive algorithms for this new equalizer architecture. We use both statistical analysis and Monte Carlo simulations to characterize the dynamic convergence of these algorithms and to compare our new structure with the conventional uncoupled SISO equalizers and fully-coupled MIMO equalizer. We show that our new equalizer outperforms the other two equalizers using a reduced computational complexity similar to the uncoupled SISO equalizers. As expected, with increasing complexity, we find that the novel RLS-based algorithms converge the fastest followed by the novel NLMS- and LMS-based algorithms. We also consider alternative packet structures and kick-start methods to increase the convergence speed and reliability of the equalizer at realistic complexity. Finally, adding multiple receiver antennas to our system, we extend our equalizer structures and algorithms to the 2 x NR case. Using analysis and simulations, we demonstrate that the added receiver diversity in this case yields even greater reliability.

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  • ADH, Aspect Described Hardware-Description-Language

    Park, Su-Hyun (2006)

    Masters thesis
    University of Canterbury Library

    Currently, many machine vision, signal and image processing problems are solved on personal computers due to the low cost involved in these computers and the many excellent software tools that exist, such as MATLAB. However, computationally expensive tasks require the use of multi-processor computers that are expensive and difficult to use efficiently due to communications between the processors. In these cases, FPGAs (Field Programmable Gate Arrays) are the best choice but they are not as widely used because of lack of experience in using these devices, difficulties with algorithmic translation and immaturity of the design and implementation tools for FPGAs. Programming languages are always evolving and the programming languages for microprocessors have evolved significantly, from functional and procedural languages to object-oriented languages. Nowadays, a new paradigm called aspect-oriented software development (AOSD) is becoming more widespread. However, hardware programming languages have not evolved to the same extent as the software programming languages for microprocessors. They are still dominated by the technologies developed in 1980s, which have significant deficiencies described in this thesis. Recent advances in HDLs (Hardware Description Languages) have taken a conservative approach based on well-proven software techniques.

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  • A Prototype Transformer Partial Discharge Detection System

    Hardie, Stewart Ramon (2006)

    Doctoral thesis
    University of Canterbury Library

    Increased pressure on high voltage power distribution components has been created in recent years by a demand to lower costs and extend equipment lifetimes. This has led to a need for condition based maintenance, which requires a continuous knowledge of equipment health. Power transformers are a vital component in a power distribution network. However, there are currently no established techniques to accurately monitor and diagnose faults in real-time while the transformer is on-line. A major factor in the degradation of power transformer insulation is partial discharging. Left unattended, partial discharges (PDs) will eventually cause complete insulation failure. PDs generate a variety of signals, including electrical pulses that travel through the windings of the transformer to the terminals. A difficulty with detecting these pulses in an on-line environment is that they can be masked by external electrical interference. This thesis develops a method for identifying PD pulses and determining the number of PD sources while the transformer is on-line and subject to external interference. The partial discharge detection system (PDDS) acquires electrical signals with current and voltage transducers that are placed on the transformer bushings, making it unnecessary to disconnect or open the transformer. These signals are filtered to prevent aliasing and to attenuate the power frequency, and then digitised and analysed in Matlab, a numerical processing software package. Arbitrary narrowband interference is removed with an automated Fourier domain threshold filter. Internal PD pulses are separated from stochastic wideband pulse interference using directional coupling, which is a technique that simultaneously analyses the current and voltage signals from a bushing. To improve performance of this stage, the continuous wavelet transform is used to discriminate time and frequency information. This provides the additional advantage of preserving the waveshapes of the PD pulses for later analysis. PD pulses originating within the transformer have their waveshapes distorted when travelling though the windings. The differentiation of waveshape distortion of pulses from multiple physical sources is used as an input to a neural network to group pulses from the same source. This allows phase resolved PD analysis to be presented for each PD source, for instance, as phase/magnitude/count plots. The neural network requires no prior knowledge of the transformer or pulse waveshapes. The thesis begins with a review of current techniques and trends for power transformer monitoring and diagnosis. The description of transducers and filters is followed by an explanation of each of the signal processing steps. Two transformers were used to conduct testing of the PDDS. The first transformer was opened and modified so that internal PDs could be simulated by injecting artificial pulses. Two test scenarios were created and the performance of the PDDS was recorded. The PDDS identified and extracted a high rate of simulated PDs and correctly allocated the pulses into PD source groups. A second identically constructed transformer was energised and analysed for any natural PDs while external interference was present. It was found to have a significant natural PD source.

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  • New Automated Industrial Technologies for Improving Chemical Penetration of Bovine Pieces in the Raw Material Processing and Conditioning Areas of Gelatine Manufacture

    Wittich, William John (2005)

    Masters thesis
    University of Canterbury Library

    The production of gelatine at Gelita N.Z. Ltd. is a time consuming process. The time limiting step in the process is the pre-treatment of the collagen tissue of the raw material in a lime/sodium sulfide solution. The liming solution breaks down the collagen in the tissue to gelatine. This is a necessary step prior to the extraction of gelatine from the hide pieces. The current liming process takes nearly 50 days to complete. Methods were investigated to increase the rate of penetration of the chemicals into the bovine hide raw material. An increase in the penetration of the liming solutions would lead to shorter processing times for this step in the process. The methods that were investigated were temperature controlled mixing, fluidization of the hide pieces and the use of ultrasound. Of all the methods tested, the fluidization of the hide pieces gave the best results. The pretreatment time of the hide pieces was reduced 9 days with this technique. Methods were also investigated to monitor the levels of conditioning in the raw material An accurate technique to measure hide conditioning was important to pilot plant trials. This helped determine how well any of the trail methods increased the penetration of chemicals into the hide pieces. The use of an ultraviolet dye proved an effective method of measuring conditioning for all the pilot plant trials. The level of chemical penetration was monitored by assessing the penetration of the UV dye. The penetration of the UV dye could be quantified by using imaging software. A possible method of monitoring conditioning in full-scale production was tested. It was determined that the glycosaminoglycans and soluble collagen released into the liming solution could be accurately measured, and related to the overall conditioning of the raw material.

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  • A Phase-Time Modulation Scheme for Peak-to-Average Power Mitigation in Multi-Carrier Wireless Transmission

    Spalding, David Ian (2006)

    Masters thesis
    University of Canterbury Library

    An explosive growth in demand for broadband mobile wireless services is currently being fuelled by cellular telephone users who, encouraged by service providers, are no longer content with voice transmission only but are demanding real-time video services, including multi-user, interactive games and 'movie' programmes. As these applications develop, expectations mount in other mobile user markets, especially the public safety arena, for comparable user features but with greater emphasis on reliability and robustness of the equipment and supporting network in adverse propagation conditions, remote locations and emergencies. These applications all have in common the requirements for efficient use of wireless bandwidth and of battery power, as well as seamless operation when moving, sometimes at high vehicle speeds, from one type of environment to another in a multi-user scenario. Orthogonal frequency-division multiplexed (OFDM) signals have been found to compare favourably with other modulation systems in these applications, the multi-carrier format being more tolerant of delay spread. It has been used in both code-division (MC-CDMA) and frequency-division (OFDMA) multi-user schemes, the latter having the advantage of maintaining orthogonality among users in fading-signal environments, with consequent simplification of signal processing. The major drawback of OFDM has been the high peak-to-average power ratio (PAPR) that is characteristic of signals with multiple sub-carriers. A result of this is that the transmitter requires a linear power amplifier (PA) that generally has to be 'backed off' to accommodate the high PAPR. Additional back-off is required to achieve linearity, as well as sometimes-complex linearisation circuitry. The power usage and cost of such a transmitter is more acceptable in a base station, tending to limit the application of OFDM to downlinks. The potential application to hand-portable terminals has severe constraints of size, cost and battery life, exacerbated by the use of video-capable LCD displays, increasing motivation for the use of MIMO (multi-antenna) technology and the development of mobile ad-hoc networks, the latter being particularly applicable in the public safety arena. Previous efforts to ameliorate the PAPR problem have been principally directed at two areas, the reduction of signal PAPR, by block coding, clipping or other techniques, and methods of achieving PA linearisation with improved power efficiency. The first object of the present research was to establish, as far as practicable, the current state of the art in these areas, to set a performance baseline. The next step was to develop an improved transmitter modulation scheme that would not only be able to take advantage of any existing peak reduction methods but would transmit a signal that would be compatible with existing OFDM receivers. A novel modulation technique is now presented, termed Quadrature Phase-Time Modulation (QPTM), that has been found to meet the requirements for linearity, simplicity and low cost, whilst being able to take advantage of constant-envelope PA technology, with its attendant power efficiency. After final amplification, the signal is restored by a passive narrow-band filter to standard OFDM form, having both phase and amplitude modulation. The QPTM system of modulation relies on a dual baseband pulse-width modulation process, performed at a substantially-higher rate than the upper baseband frequency, followed by direct quadrature modulation of a carrier signal. The work undertaken has been in the nature of a feasibility study, commencing with the theoretical basis of the technique, from which a behavioural system model was designed and simulated. After the system was simulated successfully, in several forms, a model was designed for realisation with available high-frequency integrated circuits. From this design, prototypes were constructed and tested. The prototype circuit boards also included an experimental UHF Class-D PA circuit, excluding the output filter, to facilitate ongoing development of the PA and filter subsystem as a separate project. This type of PA was seen as a potential complement to the QPTM modulator, although the technology was at an early stage of development. The prototype PA has a novel push-pull arrangement of GaAs FETs that employs a broadside-coupled tapered-stripline balun instead of the usual transformer. Preliminary measurements were made on the PA using both a spectrum analyser and a newly-available 8GHz-bandwidth digital oscilloscope to confirm basic operating characteristics. The performance of the QPTM technique at frequencies needed for broadband operation is dependent on its practical implementation, which has therefore been a major focus. The inherent difficulties in realising a highly-linear 40MHz triangle-wave reference generator, with a precise ultra-high-speed comparator and modulator system, have been overcome with the chosen design techniques and attention to several critical aspects. The result has been the successful demonstration of QPTM as an efficient PA modulation technique that is equally applicable to either narrow-band, high-capacity UHF or broadband OFDM microwave systems.

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