Engineering: Conference Contributions
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Item Open Access Understanding Poroelastic Stressing and Induced Seismicity with a Stochastic/Deterministic Model: an Application to an EGS Stimulation at Paralana, South Australia, 2011(2016) Riffault, J; Dempsey, David; Archer, R; Kelkar, S; Karra, STo create an Enhanced Geothermal System (EGS), cold water is injected at high pressure, along with acid, with the goal of reactivating pre-existing fractures and enhancing their permeability. Through increases in pore pressure and associated stress changes, shear failure occurs, which is part of the permeability enhancement process, but also results in induced seismicity. In spite of being the primary goal of stimulation, details about the spatiotemporal evolution of permeability are difficult to determine. One measure of its improvement is the increase in well injectivity, which is defined as the injected flow rate divided by the wellhead pressure. However, this measure is sensitive to both the volume of stimulated rock as well as the permeability increase, and so it does not uniquely constrain the stimulation state. To augment this analysis, we present an inverse modelling approach that incorporates both the injection records and the spatiotemporal distribution of induced seismicity. We present an application of the method to the Paralana-2 EGS stimulation undertaken in 2011 in South Australia. High pressure injection is modelled by solving coupled flow and heat transport equations in the reservoir simulator FEHM. In the model, the magnitude of permeability increase is a prescribed function of space and time. The injectivity profile observed at Paralana limits the possible set of permeability evolution scenarios, however, additional constraint is necessary to choose amongst these. As induced seismicity is a consequence of elevated pore pressure, we assume that the density of earthquake hypocenters is proportional to pore pressure rise. By comparing the pressure profiles modelled in the different scenarios to the high-resolution microearthquake data collected during the stimulation, we can pick the permeability enhancement distribution scheme most consistent with the injectivity and seismicity data.Item Open Access DESIGNING FOR UNSEEN USERS: ENHANCING NON-EXPERT RESCUERS’ EMOTIONAL EXPERIENCE IN CARDIAC ARREST EMERGENCIES(The Design Society, online-publication-date) Chen , Zhen; Zhang, Wenwen; Coutts , Euan; Li , HongyaoGlobal ageing is leading to an increase in cardiac arrest incidents among senior citizens, posing a significant societal challenge. Most out-of-hospital cardiac arrest (OHCA) incidents occur at home, limiting patients' immediate access to professional help and Automated External Defibrillators (AEDs). In such instances, Cardiopulmonary Resuscitation (CPR) by caregivers, often the patient's family with no expert knowledge of emergency care, becomes crucial. Compared to professional rescuers, caregivers could face challenges in executing effective CPR due to skill gaps and emotional barriers in performing such procedures on family members. This study investigates the emotional experience of caregivers in cardiac arrest scenarios, a critical but often overlooked aspect in the design of emergency care devices. We aim to understand 1) how emotions affect caregivers' performance and experience during domestic cardiac arrest incidents, and 2) how design can support their practical and emotional needs, enhancing their performance. Semi-structured interviews with professional rescuers and non-expert caregivers reveal the emotional challenges that caregivers might confront before, during, and after cardiac arrest incidents, such as fear of approaching a collapsed person, anxiety about causing harm, lack of confidence, and moral pressure from social ties. These challenges can lead to adverse reactions that further hinder their CPR performance. The study highlights the importance of including emotional support for non-expert rescuers in OHCA incidents. By incorporating human-centred design principles, we propose an inclusive design guideline for emergency care devices and practical design strategies to mitigate emotional barriers and assist operational performance for non-expert rescuers.Item Open Access Using Linear Assignments in Spatial Sampling(2023) Robertson, Blair; Price, C; Brown, J; Reale, MItem Open Access NZ Urban Forest Initiative(2024) morgenroth, justin; Chapman, TobyItem Open Access Detecting and measuring fine-scale urban tree canopy loss with deep learning and remote sensing(2024) Pedley D; morgenroth, justin; Pearse GItem Open Access Improving Neural Network Classification of Native Forest in New Zealand with Phenological Features(2024) Ye N; morgenroth, justin; Xu CItem Open Access Numerical modelling of the dynamic behavior of gravel-rubber mixtures and their efficiency as liquefaction countermeasures(The Japanese Geotechnical Society, 2024) Paul SM; Chiaradonna A; Chiaro, GabrieleDevastating earthquakes, such as those that recently affected Turkey and Morocco in 2023, are among the deadliest natural disasters. In addition, liquefaction-induced damage induced by strong shakings further exacerbates economic losses and elongates the repairing time for structures and infrastructures. Consequently, improving foundation soils and strengthening structural elements are possible ways to enhance the resilient capacity of a building to resist seismic forces. The main goal of this study is to numerically investigate the behaviour of innovative synthetic materials, made by a mixture of gravel and granulated rubber, used as geotechnical seismic isolation (GSI) systems relevant to the mitigation of seismic risk. To this aim, numerical simulations of a well-known and instrumented gravelly site affected by liquefaction during the 1995 Kobe earthquake are performed using a pore water pressure model implemented in one of the most popular nonlinear software adopted for dynamic analyses. The analyses were carried out with and without soil treatment made by a mixture of gravel and rubber, showing the efficacy of the proposed intervention. The result of the study contributes to expanding the knowledge about mixture-composite materials and assessing the gravel-rubber mixtures (GRMs) as an effective mitigation treatment of seismic risk.Item Open Access Liquefaction and Reliquefaction Characteristics of Compacted Slightly-Weathered Heterogeneous Tephras(The Japanese Geotechnical Society, 2024) Sood S; Chiaro, Gabriele; Wilson T; Stringer MTephras of slightly-weathered nature are essentially silty-sand deposits with no to low plasticity. They can constitute variable gradations and geochemical compositions depending upon the type and extent of weathering of particles and minerals. Case histories of liquefaction events suggest that such sand and silty-sand deposits can liquefy and reliquefy by a succeeding seismic event. However, the liquefaction and reliquefaction characteristics of different compacted tephras for backfilling usage have not been largely investigated. This paper presents the results of a series of undrained cyclic triaxial tests on specimens of three tephras(two rhyolitic and one basalt-andesitic) sourced from the North Island of New Zealand. Specimens are compacted at 90 % degree of compaction, isotropically consolidated under 100 kPa effective confining stress and then subjected to the first cyclic loading phase until liquefaction is achieved. Following liquefaction, specimens are reconsolidated and reliquefied. The test results showed an increase in the degree of compaction after reconsolidation for the compacted tephra specimens. However, a non-unified change in the liquefaction resistance is observed for the tephra specimens, which is dependent on their geochemical composition (or degree of weathering value) affecting the stress level (CSR) required. The elementally identical rhyolitic Kaharoa ashes (White Kaharoa Ash – WKA – and Golden Kaharoa Ash – GKA) exhibited a decrease in the liquefaction resistance following the first series of loading cycles. Despite a similar reliquefaction response, the liquefaction resistance of GKA was significantly lower in comparison to WKA tephra due to its more weathered nature. On the other hand, the basalt andesitic Maungataketake Ash (MA) tephra, being the most weathered out of the three tephras, showcased an opposite trend of increase in cyclic resistance after initial liquefaction.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.