Engineering: Working Papers
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Item Open Access Generalized Jacobians and explicit descents(Mathematics of Computation, 2019) Creutz BWe develop a cohomological description of explicit descents in terms of generalized Jacobians, generalizing the known description for hyperelliptic curves. Specifically, given an integer n dividing the degree of some reduced, effective and base point free divisor m on a curve C, we show that multiplication by n on the generalized Jacobian Jm factors through an isogeny ϕ : Am --> Jm whose kernel is dual to the Galois module of divisor classes D such that nD is linearly equivalent to some multiple of m. By geometric class field theory, this corresponds to an abelian covering of Ck := C xSpec k Spec(k) of exponent n unramified outside m. We show that the n-coverings of C parameterized by explicit descents are the maximal unramified subcoverings of the k-forms of this ramified covering. We present applications to the computation of Mordell-Weil ranks of nonhyperelliptic curves.Item Open Access Item Open Access Spatial data science: Closing the human-spatial computing-environment loop(2019) Adams BOver the last decade, the term spatial computing has grown to have two different, though not entirely unrelated, definitions. The first definition of spatial computing stems from industry, where it refers primarily to new kinds of augmented, virtual, mixed-reality, and natural user interface technologies. A second definition coming out of academia takes a broader perspective that includes active research in geographic information science as well as the aforementioned novel UI technologies. Both senses reflect an ongoing shift toward increased interaction with computing interfaces and sensors embedded in the environment and how the use of these technologies influence how we behave and make sense of and even change the world we live in. Regardless of the definition, research in spatial computing is humming along nicely without the need to identify new research agendas or new labels for communities of researchers. However, as a field of research, it could be helpful to view spatial data science as the glue that coheres spatial computing with problem-solving and learning in the real world into a more holistic discipline.Item Open Access Item Open Access A structural reliability framework for collapse risk assessment incorporating ground motion duration and response spectral shape(2015) Chandramohan RA structural reliability framework is developed to post-process the results of an incremental dynamic analysis (IDA) and compute a hazard-consistent collapse fragility curve. The ability to produce hazard-consistent collapse risk estimates eliminates a major drawback in the IDA procedure and brings its capabilities on par with multiple stripe analysis (MSA). The proposed framework uses two secondary ground motion intensity measures: SₐRatio which is used to quantify response spectral shape and 5- 75% significant duration (Ds₅₋₇₅). Both SₐRatio and Ds₅₋₇₅ are demonstrated to be efficient predictors of a ground motion’s collapse intensity, which is a measure of its potential to cause structural collapse. In the case of the ductile eight-story reinforced concrete moment frame building analyzed in this study, they are capable of explaining 81% of the variance in the ground motion collapse intensities. The collapse fragility curve estimated using this framework is found to compare well to the fragility curve obtained by conducting MSA using hazard-consistent ground motions. MSA is shown to represent a simulation-based approach to solve the same structural reliability problem. Finally, optimal ground motion selection strategies to produce accurate collapse risk estimates are proposed.Item Open Access Multiparameter spectral analysis for aeroelastic instability problems(2017) Pons A; Gutschmidt SThis paper presents a novel application of multiparameter spectral theory to the study of structural stability, with particular emphasis on aeroelastic flutter. Methods of multiparameter analysis allow the development of new solution algorithms for aeroelastic flutter problems; most significantly, a direct solver for polynomial problems of arbitrary order and size, something which has not before been achieved. Two major variants of this direct solver are presented, and their computational characteristics are compared. Both are effective for smaller problems arising in reduced-order modelling and preliminary design optimization. Extensions and improvements to this new conceptual framework and solution method are then discussed.Item Open Access Erosion sources and sediment pathways to streams associated with forest harvesting activities in New Zealand.(2017) Visser R; Brown, K.R.Streams and rivers are abundant in our plantation forests and the Forest Industry prides itself on protecting the intrinsic values they provide, including clean water and quality aquatic habitat. In ensuring they remain protected, the industry has both legal obligations through Resource Management Act and Regional Council requirements, as well as a professional obligation through Forest Accord agreements and the adoption of the NZFOA Environmental Code of Practice (ECoP). It is well known that forest harvesting, including the development of roads and infrastructure, can compromise these waterway values. With the law being effects-based, a clear focus should be on concentrated flows of runoff and sediment to stream channels (aka ‘breakthroughs’) that are linked to our harvesting practices. Improved knowledge about breakthroughs can be used to prescribe site-specific best management practices (BMPs) to protect water quality and aquatic habitat. To better understand how often breakthroughs occur and to identify and describe the most common breakthrough sources, the stream channels associated with 23 recent commercial forest harvests were surveyed. A breakthrough had to have the following characteristics to be recorded: evidence of scour from surface runoff and/or a concentrated trail (pathway) of sediment that reached the stream channel. Overall, there were 3.4 breakthroughs per kilometre of stream, or one breakthrough for every 6.5 hectares of harvest area, which is almost identical to studies from the Piedmont region of the southeastern United States where they found one breakthrough for every 6 to 8 hectares of harvest area. In this study, ground-based logging was associated with nearly twice as many breakthroughs as cable logging (i.e. 6.2 versus 3.3 breakthroughs per kilometre of stream) due to more soil disturbance from trails near streams. Seventy-three percent of breakthroughs were associated with concentrated runoff from roads, trails, stream crossings, and machine tracks on the hillslope. Road-stream crossing approaches delivered concentrated runoff to stream channels more often if they were associated with log truck roads and/or surface runoff could travel long distances from the adjacent and uphill road segment to the stream. Log truck roads are compact by design to support heavy loads, whereas skid trails often retained some of the protective functions of the forest floor (i.e. higher infiltration capacity). Longer road drainage lengths are associated with greater runoff volumes and velocities, thus increasing the potential for hydrologic connectivity with the stream. Conversely, where skid trail approaches to stream crossings did lead to breakthroughs, potential erosion rates were 44 times higher than those of log truck roads at stream crossings. This finding highlights the importance of closing skid trails properly upon harvest completion, especially at stream crossings. Installation of water bars and turnouts to control surface runoff and application of slash to skid trail approaches can be used to reduce the potential for sediment delivery at road-stream crossings. Overall, the level of protection provided to our waterways post-harvest is good. However, the majority of breakthroughs that were recorded could be directly attributed to operational activities and a more consistent adoption of BMPs, especially in the specific areas identified in this report, would reduce our impact even further. Common characteristics of breakthrough sources can include poor infiltration capacity, large quantities of exposed soil, and steep slopes. This project report provides specific examples (as observed in this study) of forestry practices used to reduce the frequency of sediment breakthroughs and their impacts on water quality and aquatic habitat, such as: Planning to locate roads away from streams, control road gradient and reduce earthworks Harvest planning to minimise tracking and stream crossings Installation of road drainage structures to control water in small amounts and reduce surface runoff velocity Positioning of road drainage structures to avoid direct or indirect discharges to stream channels Closure of temporary road-stream crossings that includes both water control and provisioning of immediate surface cover.Item Open Access Discussion paper - scenario analysis for the RPBC genomics programme(2016) Evison DCItem Open Access Where to next for our sinking city? Opinion piece in the Christchurch Press, 15th August 2014(University of Canterbury. Civil and Natural Resources Engineering, 2014) Quigley, M.C.; Hughes, M.W.OPINION: Associate Professor MARK QUIGLEY, from the University of Canterbury's department of geological sciences, and Dr MATTHEW HUGHES, from its department of civil and natural resources engineering, survey the changing landscape of post-quake Christchurch.Item Open Access A Simulation Model to study the performance of the HDLC protocol.(1984) McAuley, Bruce J.The aim of this project was to produce a Simula program that will model the ISO HDLC Asynchronous Balanced Mode (ABM) protocol. This program can be used firstly to provide a tool for performance evaluation of the HDLC controlled data links and secondly, to provide more insight into how the various parameters of an HDLC implementation and the data channel characteristics influence the performance.Item Open Access Queueing Models With Finite and Infinite Buffering Capacity : A Comparative Study(University of Canterbury, 1991) Anggawijaya, HerminQueueing theory offers a large variety of techniques that can be used in performance modelling of computer systems and data communication networks. The diversity of assumptions causes that the numerical results, obtained for the same system but by means of different techniques, can often be numerically very different. The project is aimed at finding common denominators for numerical results obtained with the assumption of infinite buffer capacity and that obtained with the assumption of finite buffer capacity. To be precise, this project investigates the traffic intensity regions where the approximation of queueing systems with finite buffer capacity by the queueing systems with infinite buffer capacity can be done with some amount of safety margin. The investigation includes both queueing systems with single arrivals (M/M/1, M/D/1), and a queueing system with batched arrivals (M⁽ᵇ⁾ /M/1), and two the most important characteristics of queueing systems are considered, the probability of overflow and average waiting time in the system.Item Open Access Optimising hashing functions with genetic algorithms(University of Canterbury, 1991) Botting, MarkGenetic algorithms (aka GA's) are a robust global search strategy that ignore local minima and irrelevant parameters, suitable for large search spaces. It is based on an analogy with natural evolution and survival of the fittest. A generation of potential solutions is formed by randomly mating pairs from the previous generation, giving preference to the better performers. By repeating the process many times a (near) optimal solution evolves. Hashing functions are an implementation for fast table lookup, searching, etc. Given a symbol to store or lookup in a table, a hashing function produces an index into the table, preferably such that all possible symbols will be evenly distributed throughout the table. Their effectiveness is controlled by various parameters such as table size, symbol distribution, and the form of the function itself. This project aims to couple these two areas together to optimise the parameters of a given hashing function, by searching for a good set of values for the parameters with a genetic algorithm.Item Open Access Mawd: A Collaborative Analysis Tool(University of Canterbury, 1995) Macfarlane, Justin RayVideo analysis is a powerful tool for studying human interactions. Transcribing video footage into usable and understandable data is tedious and time consuming. This report gives an overview of evaluation in RCI and CSCW, and describes the design and implementation of a Collaborative Video Analysis tool that eases data extraction and evaluation.Item Open Access Ceramic tiling viewer(1996) Burt, LanderyObserving and interacting with multi-thread programs can be difficult for the programmer. Simple input/output (I/O) can become a nightmare when multiple threads read and write simultaneously. A solution would separate the I/O streams of the multiple threads, windowing techniques can achieve this. This honours project report presents the design and implementation of Ceramic, a development tool which assists in observing and interacting with multi-thread programs. Multiple viewers (windows) can be opened to control I/0 streams of multiple threads. Ceramic has an object-oriented design based on design patterns captured from Mossenbock's OberonO viewer system. Another feature are the hierarchical tiling viewers which are a hybrid of Elastic Windows developed by Kandogan & Shneiderman. Tiling viewers have some significant advantages over overlapping windows which Ceramic has exploited.Item Open Access Identifying X-trees with few characters(University of Canterbury, 2004) Bordewich, M.; Semple, C.; Steel, M.Previous work has shown the perhaps surprising result that, for any binary phylogenetic tree T, there is a set of four characters that define T. Here we deal with the general case, where T is an arbitrary X-tree. We show that if d is the maximum degree of any vertex in T, then the minimum number of characters that identify T is log₂d (up to a small multiplicative constant).Item Open Access Post Disaster Reconstruction Research: An Industry Update(University of Canterbury. Civil and Natural Resources Engineering, 2008) Seville, E.; Myburgh, D.; Wilkinson, S.The Resilient Organisations research programme aims to improve the resilience of New Zealand organisations to major hazard events. Organisations manage, maintain and operate our infrastructure, create our economy and contribute to our society. The ability of organisations to respond effectively following a hazard event will have a large influence on the length of time that essential services are unavailable, and ultimately how well our communities cope with major disaster.Item Open Access Smart Grid in a New Zealand Context(University of Canterbury. Electrical and Computer Engineering, 2012) Lapthorn, A. C.The following report examines the Smart Grid in the context of New Zealand. It begins by developing a definition for what the Smart Grid actually by looking at various international organisations views. Defining the Smart Grid as a modernisation of the existing system to improve efficiency and reliability and that it will be a gradual process of time that has already begun. The report then goes on to look at Smart Grid progress around the world. It examines work in North America, Europe, Asia and Australia. By examining the government policies around Smart Grids and the various pilot projects that have been implemented globally, a better understanding the progress New Zealand has made can be achieved. A major point that has been noted in this work is the shear size of the investment and resources that have already used in the Smart Grid arena. The next section of the report looks at international standards development. The focus is on work carried out by the International Electrotechnical Commission the National Institute of Standards and Technology in North America. Both these organisations have developed a Smart Grid standards roadmap outlining a number of current standards applicable to Smart Grids, identifying the gaps in the standards portfolio and developing plans to address those shortcomings. The report then goes on to examine current Smart Grid progress in the New Zealand context. The various different sectors in the New Zealand electricity industry are examined individually including government, generation, transmission, distribution and retail. The findings show there is already good progress in Smart Grid related goals such as renewable energy generation and peak load management. However, there is still some work needed for aspects such as AMI standardisation. The report then finishes with a discussion and concluding remarks.Item Open Access Barriers to Post Disaster Reconstruction: Report on Workshop(Resilient Organisations, 2006) Le Masurier, J.; Seville, E.A workshop was held to identify the challenges and barriers to post-disaster reconstruction in New Zealand to help guide research under Objective 3 of the Resilient Organisations project. The workshop brought together people with relevant experience in post-disaster reconstruction and/or specialist knowledge of the regulatory, legislative and contractual issues that could influence reconstruction. A list of attendees is given in Appendix A. This report summarises the key issues from the workshop and develops these issues into research directions. On the basis of both student and funding resources available, the report identifies the research that will be carried out as part of the current FRST funded research project. Other research from the priority list could potentially be carried out in the future if further research resources become available. The report is organised into the four key areas considered during the workshop: legislative and regulatory issues, coordination of reconstruction, contractual issues and resource issues.Item Open Access Resourcing the Canterbury Rebuild: Changes and Emerging Themes(University of Canterbury. Civil and Natural Resources Engineering, 2012) Chang-Richards, A. Y.; Wilkinson, S.; Seville, E.The second quarter of 2012 has seen a clearer plan for the recovery of Christchurch over the next few years. The targeted Government’s agenda involves a $5.5 billion 2012 Government Budget 1 and the creation of a new Christchurch Central Development Unit2 to lead the rebuild of Christchurch Central. This in turn enables the organisations involved in the rebuilding of Christchurch to start finding efficiencies as part of their resourcing plansItem Open Access Preliminary Results from Organisational Resilience and Recovery Study December 2010(University of Canterbury. Civil and Natural Resources Engineering, 2010) Kachali, H.; Stevenson, J.; Whitman, Z.; Seville, E.; Vargo, J.; Wilson, T.The Resilient Organisations Research Programme and the University of Canterbury are undertaking a longitudinal study to examine the resilience and recovery of organisations within the Canterbury region following the 4 September Canterbury earthquake. The preliminary data suggest the physical, economic and social effects of the earthquake were varied across industry sectors within Canterbury. These preliminary results catalogue organisations’ perceptions of the: - disruptions to their ability to do business - challenges faced in the aftermath of the earthquake - factors that have helped mitigate the effects of the earthquake - revenue changes and projections for the duration of this change - financing options for recovery