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    Quantifying bed stability : the missing tool for establishing mechanistic hydrological limits : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Geography at Massey University, Palmerston North, New Zealand
    (Massey University, 2018) Neverman, Andrew J.
    Sediment transport processes are a key mechanism of ecological change in riverine systems, and certain levels of sediment flux are necessary for healthy ecosystem functioning. Altered flow regimes and sediment mobility are contributing to a global problem of higher substrate embeddedness reducing the frequency of substrate scour events and leading to increases in periphyton accrual. Excess periphyton accrual leads to fish and invertebrate kills from oxygen depletion, degraded ecological health, altered sediment dynamics, deterioration in water taste, and odour nuisance. In recent decades, reports of toxic periphyton proliferations have increased and are linked with health problems in humans including asthma, skin rashes, liver damage, and the death of domestic dogs. Excess periphyton accrual is prominent in impounded catchments where dams have a considerable impact on flow and sediment regimes. With at least 3,700 large dams currently under construction or in the planning phase the problem is set to increase in the foreseeable future. Hydrological limits are widely implemented by authorities in an attempt to manage periphyton accrual. Hydrological limits are frequently based on flow-ecology relationships but are often ineffective. Sediment transport thresholds have been found to have a better relationship with periphyton accrual than hydrological metrics. Flow-ecology relationships do not account for the mechanisms of periphyton removal (scour, abrasion, and molar action) which are likely to vary between sites at equivalent flows, and the species-specific resistance to each mechanism also likely varies. Abrasion and molar action result from transport of sediment. Improving the effectiveness of hydrological limits as a tool for river management therefore relies on setting flows with the aim of inducing sediment transport to initiate mechanisms of periphyton scour. This will require models which can accurately predict the flow required to induce different phases of sediment transport. The research presented in this thesis focuses on improving the estimation of gravel entrainment to advance entrainment models as a means of setting hydrological limits to induce molar action and improve the effectiveness of periphyton removal. A literature review of methods for estimating gravel particle entrainment thresholds in natural channels revealed a considerable gap in methods being available to quantify substrate characteristics to calculate resistance thresholds. The review also found significant challenges in identifying the onset of gravel transport in natural channels, and difficulty obtaining corresponding hydrodynamic data to identify entrainment thresholds. Further, the review found seepage was an important component of hydrodynamic forces for inducing particle entrainment in flumes, but seepage is not considered in conventional entrainment formulae, and is not measured alongside bedload transport data in the field. A suite of tools is identified and developed to improve the quantification of substrate structure and resistance, identification of incipient motion, and quantification of entrainment thresholds in natural gravel beds to advance the assessment of bed mobility. Optical and ranging techniques are compared to identify an optimal approach to remotely quantify substrate structure. Both approaches were found to produce a comparable quantification of surface roughness using point cloud elevations, but identified different trends in surface layer development. Quantification of surface layer development was found to be sensitive to the cell size used to grid the data, and this sensitivity increased with higher-order statistical moments which were used to describe armouring. Airborne optical sensors were found to be the most versatile method for remote characterisation of gravel-bed surface structure, with a larger range of metrics being derivable from the same dataset to quantify a wider range of substrate structural and textural characteristics. Whilst quantifying bed structure is critical for developing bed mobility models, measuring the resistive force of the bed created by the structural arrangement of particles is required for model calibration and empirical data collection. A protocol was developed to use a modified penetrometer to quantify the resistive force of the armour (active) layer in gravel-bed channels. The modifications made to the penetrometer made it sensitive to variations in armour layer compactness, and allowed for adaptive penetration depths enabling variations in armour layer thickness to be accounted for. The protocol and modified penetrometer provide a significant advancement in the ability to empirically quantify bed resistance and relate bed structure to potential bed mobility, and build on the remote sensing methods to provide a suite of bed resistance parameters for entrainment models. Measurement of bed mobility is also critical for calibrating entrainment models and relating ecological metrics to bed mobility thresholds. Both direct and indirect measurement of bed mobility have benefits for research and river management. Tick-box indices are frequently used in ecological studies to provide an indirect assessment of substrate (in)stability (i.e. bed mobility). These indices often provide a poor approximation of bed mobility, and do not relate well with biotic communities, but their low-cost and rapidity make them a valuable tool for research and management. An improved index is developed to provide rapid, low-cost assessment of bed mobility. This index improves on previous methods by focusing on objective measurements of parameters where low-cost approaches are available, or providing a framework for scoring parameters where visual assessment is required. The index scores correlated well with tracer particle data, and were found to relate to accrual of Phormidium biomass. This index therefore provides a means to rapidly and cost-effectively estimate bed mobility and predict periphyton accrual. Direct measurement of bed mobility is also required to provide an empirical dataset for the calibration of particle entrainment and transport models, and for the empirical derivation of hydrological limits. A multi-sensor system was developed to measure the onset of particle movement, and record corresponding hydrodynamic data, including bed seepage, to identify hydraulic entrainment thresholds in natural channels, and therefore address the challenges of identifying bedload entrainment thresholds identified in the literature review. A pilot study testing the system identified bed seepage and turbulence intensity as key predictors of particle entrainment, and discharge and mean velocity as the worst predictors. These findings challenge the use of discharge and mean velocity as the metrics used to set hydrological limits if mechanistic limits based on bed mobility-ecology relationships are to be established effectively. These tools provide a means for scientists to study bedload entrainment and transport, identify their thresholds, and relate the frequency and magnitude of these processes to benthic community dynamics. This research will form the basis for establishing the mechanisms required to achieve removal of excess periphyton and establish hydrological limits to ensure these mechanisms function and effective removal of periphyton is achieved to maintain ecosystem health.
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    Analyzing seismic signals to understand volcanic mass flow emplacement : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Sciences at Massey University, Palmerston North, Manawatu, Aotearoa New Zealand
    (Massey University, 2017) Walsh, Braden Michael Larson
    Natural hazards are one of the greatest threats to life, industry, and infrastructure. It has been estimated that around a half billion people worldwide are in direct proximity to the danger of volcanic hazards. For volcanic mass flows, such as pyroclastic density currents and lahars, extreme runout distances are common. The close proximity of large population centers to volcanoes requires the implementation of early warning and realOtime monitoring systems. A large portion of the progress towards realOtime monitoring is through the use of geophysical instrumentation and techniques. This research looks into emerging geophysical methods and tries to better constrain and apply them for volcanic purposes. Specifically, multiple types of amplitude source location techniques are described and used for locating and estimating the dynamics of volcanic mass flows and eruptions. Other methods, such as semblance and back projection, are also employed. Applying the active seismic source method to a lahar that occurred on October 13th 2012 at Te Maari, New Zealand, locations and estimations of lahar energy were calculated in an increased noise environment. Additionally, the first ever calibration of the amplitude source location (ASL) method was conducted using active seismic sources. The calibration proved to decrease true error distances by over 50%. More calibration on the ASL method was accomplished by using all three components of the broadband seismometer. Initial results showed that using all three components reduced extreme errors and increase the overall precision of the locations. Finally, multiple geophysical methods (ASL, semblance, back projection, waveform migration, acoustic-seismic ratios) were used to show that a combination of instrumentation could produce more reliable results. This research has filled gaps in the preexisting knowledge for hazards. With these results, more effective hazard warnings can be produced, and systems for real time estimations of locations and dynamics of volcanic events could be developed.
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    TreeScan V and frame mosaicing : thesis submitted in partial fulfilment of the requirements of the Masterate Degree in Information Engineering, Department of Production Technology, Massey University
    (Massey University, 1997) Nourozi, Farshad
    In 1993 the Department of Production Technology carried out a feasibility study of applying digital imaging technology in the pre-harvest inventory assessment for the forestry industry. Consequently a scanning mechanism was developed to capture a series of overlapping images along the stem of a tree. These overlapping images needed to be registered and combined to form a single long and thin high resolution image of the tree. This report describes different methods of finding the overlaps between the consecutive images. Algorithms developed here fall into two broad categories: Spatial Domain and Frequency Domain feature matching. Comparison of different algorithms is made and advantages and disadvantages of each one are discussed. Finally a robust algorithm is developed which combines the strengths of the other algorithms.
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    CMOS radiation sensor design in 130nm CMOS technology : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Electronics and Computer Engineering at School of Engineering and Advanced Technology, Massey University, Albany Campus
    (Massey University, 2017) Zhang, Chaoping
    This research work deals with a CMOS radiation sensor design, which covers a new open source floating-gate MOSFET (FGMOSFET) device model for analog circuit design, Floating Gate Radiation Field Effect Transistor (FGRADFET) design, FGRADFET sensor output circuit design and their layout implementation using the 130nm IBM CMOS process. At first, a new FGMOSFET device model to facilitate circuit design is presented. In this model, the floating gate is charged by the Fowler-Nordheim tunneling effect. The equations representing the new device model were explored and verified on MATLAB. Verilog-A script was employed to transfer the equations and build the complete device model. The new FGMOSFET circuit model was plugged-in as a pop-up menu component in a standard 130 nm CMOS technology design library so that it can be instanced directly on a schematic editor palette for analog circuit simulation and design in a similar fashion as the standard MOSFET devices. Furthermore, the thesis describes the radiation sensor of FGRADFET that has an extra silicon area (125μm×200μm) as an antenna to sense the radiation from the environment. There are 16 PMOS transistors (1μm×2μm each) beneath the edge of the antenna to charge the floating gate. A radiation sensor readout circuit is also designed for this sensor. This circuit includes differentiator, pre-amplify buffer, chopper amplifier, low-pass filter and single-ended output amplifier. This integrated dosimeter has a 3.205mW power consumption and 2.33mGy- 23mGy measuring range (The single-ended output voltage changes from 26mV to 967mV), which could be used for tremendous radiation exposure applications such as radiation therapy.
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    Development of an in-field tree imaging system : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology at Massey University
    (Massey University, 1996) Weehuizen, Marijn
    Quality inventory information is essential for optimal resource utilisation in the forestry industry. In-field tree imaging is a method which has been proposed to improve the preharvest inventor assessment of standing trees. It involves the application of digital imaging technology to this task. The method described generates a three dimensional model of each tree through the capture of two orthogonal images from ground level. The images are captured and analysed using the "TreeScan" in-field tree imaging system. This thesis describes the design, development, and evaluation of the TreeScan system. The thesis can also be used as a technical reference for the system and as such contains appropriate technical and design detail. The TreeScan system consists of a portable computer, a custom designed high resolution scanner with integral microcontroller, a calibration rod, and custom designed processing software. Images of trees are captured using the scanner which contains a CCD line scan camera and a precision scanning mechanism. Captured images are analysed on the portable computer using customised image processing software to estimate real world tree dimensions and shape. The TreeScan system provides quantitative estimates of five tree parameters; height, sweep, stem diameter, branch diameter, and feature separation such as internodal distance. In addition to these estimates a three dimensional model is generated which can be further processed to determine the optimal stem breakdown into logs.