Engineering: Conference Contributions
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Item Open Access Fourier Series Model for Facial Feature Point Land-Marking(Elsevier BV, 2023) Arabian H; Ding N; Chase, Geoff; Moeller KThe field of digital health apps, combined with intelligent learning systems, is new and expanding to incorporate a wide range of possibilities in different domains. An application in the field of digital therapy is for the incorporation of emotion recognition systems as a tool for therapeutic interventions. Adopting an individually tailored virtual world combined with a novel reward system in a gaming scenario, complemented with the technical affinity of most autism spectrum disorder (ASD) children makes a suitable atmosphere for therapeutic intervention. In this paper the use of image processing techniques coupled with Fourier models is used to generate point land-mark annotations on facial features in an image. The OULU-CASIA database was used for the analysis process. The images were first pre-processed based on previous work to reduce background noise and focus on the face. Afterwards a de-correlation stretch was executed to separate different features. A series of morphological, region detections and boundary traces followed. Fourier series models were used to transition the rough segmented pixel data into a smooth geometric representation. Twenty evenly distributed land-mark points are then selected from a fine mesh. Results showed that the geometric representation adhered to the segmented pixel data with a mean of 81.88% Dice similarity. The positive outlook highlighted the effectiveness of such a technique in automating the land-mark annotation process, which is tedious and time consuming. This method leads to explainable machine learning feature representations, which lead to more robust emotion recognition models.Item Open Access Examining the effect of sap sugar concentration on fibre embolism in sugar maple (Acer saccharum)(International Society for Horticultural Science (ISHS), 2024) Robinson , J. A.; Rennie , M.; Clearwater , M.; Holland , D. J.; van den Berg , A.; Watson, MatthewSugar maple (Acer saccharum) develops elevated pressures in response to repeated cycles of freezing and thawing. This pressure is theorised to develop due to compression of gas present within fibres. Due to surface tension the pressurised gas within fibres should rapidly dissolve. That the gas persists over time is believed to be due to an osmotic barrier present between fibres and vessels that prevents sucrose from diffusing into fibres. This creates sufficient osmotic pressure to prevent gas dissolution and so maintain fibre embolisms. In our work we examine this hypothesis using synchrotron based microCT to produce high-resolution three-dimensional images of stem segments. Using this technique, we directly resolved the gas present in the fibres. Subsequently we perfused stem segments with either water or 2% sucrose and re-imaged them to examine any changes in fibre embolisms. Additionally, we also looked at samples that were frozen for 2-3 months to promote fibre embolism development, and for comparison we look at paper birch (Betula pendula), a species that is thought to develop elevated stem pressures through a different mechanism than Acer. From the fresh stem segments, we observed fibre embolisms were indeed present, and that when perfused with sucrose solution there was little to no change in fibre embolisms, whereas in almost all cases perfusing with water led to partial or complete refilling of fibre embolisms, supporting the hypothesis. The frozen samples did not display complete xylem embolization, in contrast to expectations, and showed complete refilling upon perfusion with either solution, suggesting cell damage had occurred. The birch samples also showed fibre embolisms. These embolisms remained after perfusing with sucrose solution, and there was some evidence the fibre embolisms refilled upon perfusion with water, however more samples are required to confirm these observations.Item Open Access Sensor-Based Pavement Layer Change Detection Using Long Short-Term Memory (LSTM)(IOP Publishing, 2022) Patel , Tirth; Guo, Hongwei; Zou , Yang; van der Walt, Jacobus Daniel; Li, YuDuring construction, pavement projects often suffer from a lack of progress certainty, which leads to cost and time overruns. The pavement construction progress should be monitored in a timely and accurate manner to provide prompt feedback and ensure project success. However, current pavement construction progress monitoring practices (e.g., data collection, processing and analysis) are manual, time-consuming, tedious, inconsistent, subjective and error-prone. The previous research study was limited to only incremental road construction progress measurement. This preliminary study proposes a novel sensor-based method to identify pavement layer changes during construction using a time series algorithm for the approach development of automated as-built measurement of road construction. In this study, data were collected from generating various road construction scenarios in a controlled environment by simulating layer changes using a ground vehicle equipped with a laser ToF (time-of-flight) distance-ranging sensor. Subsequently, Long Short Term Memory (LSTM) was utilized on collected data for feature detection as 'layer up', 'layer down' and 'layer not changed' to classify road layer change. The experimental result demonstrates 84.91% as a promising overall average accuracy of road layer change classification on the control environment data, confirming the potential implementation suitability to detect pavement layers in real pavement construction projects. However, low-performance measures (low precision, recall and F1 score) of layer up and layer down suggest further improvement to enhance the robustness of the proposed model. This method can be extended to automate pavement construction progress monitoring by validating the proposed approach in a real case.Item Open Access Buckling Restrained Braces - Issues and Solutions(2023) MacRae , G. A.; Lee, Chin-LongThis paper describes some design issues relating to buckling restrained braced frames (BRBFs) including: (i) BRB system capacity under both axial compression and out-of-plane (OOP) frame deformations, (ii) BRB demand estimation, (iii) brace inertial effects, (iv) gusset plate (GP) weld strength, (v) frame element requirements near the gusset plate, (vi) frame ratchetting considerations, (vii) frame demands, (viii) load paths into the frame, and (ix) BRB quality control. Methods to address these issues are proposed. As part of this, a simple method for BRB system design considering BRB stability and frame out-of-plane deformation effects is described. The method seeks to prevent yielding in the BRB system except for within the core inside the BRB restrainer/casing. It uses standard equations with which engineers are familiar. The method discourages brace/gusset plate regions which are too flexible (where instability may occur as a result of axial force), or which are too stiff (where yielding may occur due to out-of-plane frame deformations thereby compromising the performance in later in-plane deformation cycles).Item Open Access Effect of the stress-dependency and anisotropy of unbound granular base and subgrade materials on the TSD deflection slopes(2024) Kazemi N; Saleh, Mofreh; Lee, Chin-LongThe Traffic Speed Deflectometer (TSD) is a mobile vehicle that utilizes Doppler laser sensors to capture pavement surface deflection velocities. These velocities are then divided by the travel speed to obtain deflection slopes, which are used in pavement management tasks. Previous studies on pavement layer moduli back calculation using TSD have often overlooked the nonlinear stress-dependency and anisotropy of pavement layers materials. This research, employing ABAQUS finite element software, explores the impact of stress-dependency and anisotropy of unbound granular materials and fine-grained soil layers on TSD deflection slopes. Simulations of a 2D-axisymmetric pavement system, considering specific material properties and layer thicknesses under uniform tire loading, reveal a substantial difference of about 40% variation in deflection slopes when nonlinear stress-dependency is considered. Comparatively, considering an anisotropy ratio of 0.5 or higher maintains deflection slope differences around 10%, while an anisotropy ratio below 0.5 leads to a 40% variation. This study emphasizes that overlooking stress-dependency and anisotropy of pavement layers materials in analyzing TSD data in pavement layers’ back calculation is inadequate.Item Open Access Numerical Simulations of the FWD and TSD Loading and the Effects on Pavement Surface Deflection(2024) rith, makara; Saleh, MofrehPavement surface deflection is essential to assess the structural performance of the pavements and for the design of most suitable rehabilitation strategies. Various deflectometer devices can extract those deflections, however, in different manners. Falling-Weight Deflectometer measures surface deflection from the impulsive and stationary load. Traffic Speed Deflectometer, in contrary, simultaneously records deflection data under vehicle-moving speed. Many studies reported the different responses from FWD and TSD under simple assumptions. Additionally, even though both devices utilize unidentical loading pattern, the deflection data is still interpreted by the same radial location, indices, and curvature. This study aimed to compare the outcomes from FWD and TSD loading by looking into the fully surface deflections and other responses under various scenarios. This comparison was numerically conducted by 3D Finite Element Method. Dynamic effect, and time-temperature dependent material. behavior were considered in the analysis. The effect of pavement thickness, material, roughness, and speed were also discussed.Item Open Access Critical Assessment of Mammography Accuracy(Elsevier BV, 2023) Fitzjohn , Jessica; zhou, cong; Geoffrey Chase , J.Mammography is currently considered the gold standard for breast screening, despite painful breast compression, invasive radiation exposure and excessive infrastructure and personnel requirements, contributing to its inequity. Furthermore, sensitivity and specificity of mammography are often overstated by studies utilising flawed methodology. This paper critically reviews the literature reporting on methods used to calculate diagnostic accuracy of mammography. Values for sensitivity, specificity and receiver operator characteristic (ROC) curve area (AUC) are presented by averaging results from studies inclusive of a comparison to another breast screening modality. The result is mammography sensitivity of 60%, specificity of 80%, AUC of 0.73. These values should be used when assessing diagnostic performance of other breast screening technologies.Item Open Access Small-strain shear stiffness of sand-gravel mixtures(2023) Pokhrel , Abilash; Chiaro, GabrieleSmall-strain shear stiffness (G0) is a key parameter for seismic ground response analysis and performance evaluation of various earth structures and foundations. To account for its pressure and density dependency, G0 has been conveniently correlated to mean effective stress (σm′) and void ratio (e). Such an approach is suitable for conventional uniform materials. However as found in this study, it is not always applicable to estimate the G0 of sand-gravel mixtures (SGMs), because it essentially fails to account for the combined effects of density and gravel content (GC). In this study, aimed at addressing this issue and developing a theoretical framework and empirical correlations suitable for estimating the G0 of SGMs, a series of bender element laboratory tests were carried out on selected SGMs. Specifically, SGMs were obtained by mixing two clean sands – namely New Brighton Sand (mean diameter, D50 = 0.2 mm) and Dalton River Washed Sand (D50 = 0.75 mm) – and rounded pea gravel (D50 = 5.5 mm). Shear wave velocity of specimens having GC = 0, 10, 25, 40 and 60% and prepared at a relative density (Dr) of 20, 30, 45 and 60% was measured at σm′ = 50, 100, 150 and 200 kPa. The laboratory results indicated that G0 of SGMs increases with increasing both the Dr and σm′, whereas the effect of GC would be marginal to significant depending on the limiting and threshold sand contents. To correlate G0 simultaneously with both GC and Dr, the equivalent void ratio (ef(eq)) was adopted. It is shown that the use of e f(eq) makes it possible to uniquely describe the G0 of SGMs for any combination of GC and Dr over the full range of σm′ level applied in this study.Item Open Access Pre-Trained Language Models Represent Some Geographic Populations Better than Others(ELRA and ICCL, 2024) Dunn , Jonathan; Adams, Benjamin; Madabushi , Harish Tayyar; Calzolari N; Kan M-Y; Hoste V; Lenci A; Sakti S; Xue NThis paper measures the skew in how well two families of LLMs represent diverse geographic populations. A spatial probing task is used with geo-referenced corpora to measure the degree to which pre-trained language models from the opt and bloom series represent diverse populations around the world. Results show that these models perform much better for some populations than others. In particular, populations across the US and the UK are represented quite well while those in South and Southeast Asia are poorly represented. Analysis shows that both families of models largely share the same skew across populations. At the same time, this skew cannot be fully explained by sociolinguistic factors, economic factors, or geographic factors. The basic conclusion from this analysis is that pre-trained models do not equally represent the world’s population: there is a strong skew towards specific geographic populations. This finding challenges the idea that a single model can be used for all populations.Item Open Access Urban forest canopy cover goals – an exploration of current practices(2024) morgenroth, justinItem Open Access Gravel-rubber mixtures: macro- and micro-scale engineering properties.(2023) Chiaro, GabrieleIn this paper, selected laboratory test results for GRMs are presented, and the influence of adding granulated rubber on the macro-scale engineering properties (i.e., compaction, compressibility, shear strength, energy absorption, small-strain shear stiffness and dynamic properties) of GRMs are described. Then, using the newly developed DEM4GRM model, the force anisotropy, load-transfer mechanism and strong-force network at the particle-to-particle scale are examined and the change in skeleton material from stiff gravel-like to soft rubber-like is described.Item Open Access Simulating Solar Storms via Active DC Injection from the HVDC Link(2023) Lapthorn, Andrew; Hardie , Stewart; Agger , Paul; Subritzky , Soren; Dalzell , Mike; Clilverd , Mark; Cobbett , Neil; Beggan , Ciaran; Huebert , Juliane; Eaton , Eliot; Brundell, James; Rodger , CraigAs part of the MBIE Endeavour programme “Solar Tsunamis: Space-Weather Prediction and Risk Mitigation for New Zealand’s Energy Infrastructure,” we are interested in the effects of geomagnetically induced currents (GICs) on New Zealand’s electrical infrastructure. GICs appear as quasi-dc currents on the power system and can lead to problems in the network as a result of transformer saturation such as increased reactive power demand, increased harmonics, and even overloading of the transformers. Studies have shown that, depending on the severity of the solar storm, these effects could potentially be widespread. Different transformer designs behave differently under these quasi-dc conditions, with single phase designs the worst, and three-limb core designs proving the most resilient. Furthermore, several transformers in New Zealand have neutral earthing resistors (NERs) installed. Therefore, it is difficult to say at what point do GICs start becoming a problem, and how much current is too much current. In January 2023, with the support of Transpower, we were able to utilise New Zealand’s high voltage DC (HVDC) link to inject current directly into the ground at Haywards substation and monitor the effects on two 216 MVA, 220/110 kV autotransformers, along with monitoring of associated transmission lines. Over the span of nine days, six injection tests were carried out lasting between one and two hours each time. The peak current injected into the ground was about 621 A. This paper provides an overview of the testing plan, procedure, and initial results from the collected data.Item Open Access NZ Perspective on Urban Forests(2024) morgenroth, justinItem Open Access An Overview of the Unique DC Injection Campaign for Replicating GICs on High Voltage Transformers in New Zealand(2023) Lapthorn, Andrew; Hardie S; Subritzky S; Dalzell M; Clilverd M; Cobbett N; Beggan C; Huebert J; Eaton E; Brundell J; Rodger CIntroduction: Between 21 and 29 January 2023, with the assistance of Transpower, we successfully utilised New Zealand's HVDC link to directly introduce current into the ground at Haywards substation. Our objective was to simulate the efffects of geomagnetically induced currents (GICs) and observe their impact on two 216 MVA, 220/110 kV autotransformers and one 80 MVA transformer, as well as to monitor the associated transmission lines.Item Open Access Optimising Tree Responses to Root Pruning in Mature Trees: An Introduction to Some New Research(2023) Benson A; morgenroth, justinItem Open Access Non-Fungible Programs: Private Full-Stack Applications for Web3(2024) Regalia, Blake; Adams, Benjamin; Vallarano N; Tessone CJThe greatest advantage that Web3 applications offer over Web 2.0 is the evolution of the data access layer. Opaque, centralized services that compelled trust from users are replaced by trustless, decentralized systems of smart contracts. However, the public nature of blockchain-based databases, on which smart contracts transact, has typically presented a challenge for applications that depend on data privacy or that rely on participants having incomplete information. This has changed with the introduction of confidential smart contract networks that encrypt the memory state of active contracts as well as their databases stored on-chain. With confidentiality, contracts can more readily implement novel interaction mechanisms that were previously infeasible. Meanwhile, in both Web 2.0 and Web3 applications the user interface continues to play a crucial role in translating user intent into actionable requests. In many cases, developers have shifted intelligence and autonomy into the client-side, leveraging Web technologies for compute, graphics, and networking. Web3’s reliance on such frontends has revealed a pain point though, namely that decentralized applications are not accessible to end users without a persistent host serving the application. Here we introduce the Non-Fungible Program (NFP) model for developing self-contained frontend applications that are distributed via blockchain, powered by Web technology, and backed by private databases persisted in encrypted smart contracts. Access to frontend code, as well as backend services, is controlled and guaranteed by smart contracts according to the NFT ownership model, eliminating the need for a separate host. By extension, NFP applications bring interactivity to token owners and enable new functionalities, such as authorization mechanisms for oracles, supplementary Web services, and overlay networks in a secure manner. In addition to releasing an open-source software development kit for building NFPs, we demonstrate the utility of NFPs with an interactive Bayesian game implemented on Secret Network.Item Open Access Canopy Cover Dynamics in New Zealand’s Cities(2023) morgenroth, justinItem Open Access Very Low Frequency Observations During an Active DC Injection Campaign that Simulated Geomagnetic Storm effects on High Voltage Transformers(2023) Clilverd M; Cobbett N; Brundell J; Dalzell M; Lapthorn, Andrew; Hardie S; Agger P; Subritzky S; Beggan C; Huebert J; Eaton E; Rodger CIn January 2023, in collaboration with our industry partner Transpower Ltd (New Zealand’s national grid operator), a campaign was undertaken to inject large currents into operating high voltage transformers. New Zealand’s high voltage DC (HVDC) link was used to inject current directly into the ground at Haywards substation near Wellington, including into several 216MVA 220 kV / 110 kV autotransformers. Six injection test periods occurred, each lasting 1-2 hours. The peak current injected into the ground was about 621 A, spread across several transformers within the Haywards substation. The injection campaign was undertaken for New Zealand’s Endeavour programme “Solar Tsunamis: Space-Weather Prediction and Risk Mitigation for New Zealand’s Energy Infrastructure”. The technique of substation monitoring using nearby very low frequency (VLF) receivers has been previously reported by the lead author, based on observations of the Halfway Bush substation (HWB) in Dunedin, New Zealand. Evidence of harmonic distortion through enhanced odd and even 50 Hz harmonic amplitudes during geomagnetically induced current (GIC) events of up to 50 A, associated with large geomagnetic storms in 2017 and 2018, have already been observed and analysed in detail. Typically, enhancements in the amplitude of harmonics in the 100 Hz to 600 Hz range have been detected during GIC events. The VLF observations from HWB are consistent with the idea that the local transformers radiate even harmonics of the 50 Hz fundamental mains frequency due to half-cycle saturation driven by additive dc flux induced by GIC. During the Active Injection campaign at Haywards Station, two identical VLF receiving systems were deployed around the substation. Each VLF system comprised a set of orthogonal magnetic field loop aerials. Preliminary results from the VLF harmonic data suggest that observed variations in amplitude in the 100 – 600 Hz frequency range were correlated with temporal variations in the injected ground current, particularly after the current had been applied for more than 20 minutes. Prior to that, a slow increase in harmonic distortion occurred, beginning at the time of the injection onset. For injected substation earth currents ranging from 300 A – 600 A (about 20 A – 35 A for individual autotransformers) even small variations of the order of 10’s of amps appeared to be well correlated with the VLF amplitude variations of even order harmonics. In this study we present the VLF data during the injection events, describing the responses observed from a large, complex substation experiencing geomagnetic storm-like effects.Item Open Access A displacement-based design method for low-damage dual systems with hysteretic and nonlinear viscous energy dissipation(2023) Gu, A.; Rodgers, Geoffrey; Henry, R. S.In 2019, a large shaking-table test was performed for a full-scale two-storey low-damage concrete wall building. The test building comprises unbonded post-tensioning (UPT) rocking walls and perimeter frames in both directions. The perimeter frames incorporated hysteretic energy dissipation devices at slotted-beam connections at the beam-column and beam-wall joints, so that both UPT walls and perimeter frames would resist seismic action in parallel as a low-damage dual system. High force-to-volume (HF2V) lead-extrusion dampers and nonlinear viscous dampers (NVDs) were adopted in the test building. This experimental test building was used as the basis for a parametric computational study in OpenSees, where a range of structural parameters were modified, including number of stories, wall- strength contribution ratios, effective period, and equivalent damping ratio. A displacement-based design method is proposed for the application of the low-damage dual system with energy dissipating device combination and compared against the computational results. Nonlinear time-history analyses (NLTHAs) were conducted to validate the methodology, and key response parameters from the time-histories are compared with the design values, to validate the proposed displacement-based design process. The global responses of the NLTHAs validated the proposed design process for both coupled and decoupled dual systems, with the average absolute relative error of the roof drift being 7.94%, considering NVDs’ EVD determined by the power approach. However, the proposed design process was shown to significantly underestimate the roof drift responses of the decoupled dual system when the wall strength portion was smaller than 0.7.Item Open Access Learning Software Quality Assurance with Bricks(IEEE, 2021) Morales Trujillo MESoftware Quality Assurance (SQA) and Software Process Improvement (SPI) are topics of crucial importance for software engineers; however, teaching them in a lecture room comes with several limitations due to lack of practical experience. With that in mind, we created KUALI-Brick, a LEGO-based activity that brings SQA and SPI concepts together applying them in order to successfully build a LEGO city. This hands-on activity has been carried out in a fourth-year Software Engineering course at the University of Canterbury, with current results showing high levels of fun, increased engagement and an improved learning experience. We present a step-by-step guide to replicate the activity as well as lessons learned after conducting the activity for three consecutive years.