Engineering: Journal Articles

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  • ItemOpen Access
    Evaluation of alternative carbon accounting categories for forestry in Gisborne District under the Emissions Trading Scheme
    (2022) Manley, Bruce; Xu , Cong (Vega); Visser , Rien
    In 2022, as part of Management Case Study, final-year Bachelor of Forestry Science students at the University of Canterbury re-mapped the small-scale forest estate in Gisborne District, estimated the delivered wood cost (DWC) at the time of harvesting and assessed the likelihood of harvesting. They also evaluated the profitability of afforestation under different carbon accounting approaches and categories.
  • ItemOpen Access
    Bandgap engineering of α-(AlxGa1-x)2O3 by a mist chemical vapor deposition two-chamber system and verification of Vegard's Law
    (AIP Publishing, 2018) Dang, Giang; Yasuoka T; Tagashira Y; Tadokoro T; Theiss W; Kawaharamura T
    This work reports growth of α-(AlxGa1-x)2O3 single crystals with high incorporation of Al by a Mist Chemical Vapor Deposition two-chamber system, which was rationally designed to avoid side-reactions between different precursors during solution preparation for multi-component thin film growth. Multiple acceleration voltages were used in Energy Dispersive X-ray measurements to reliably obtain the Al composition x of the films. As a result, Vegard's law for lattice constants was verified and found to be valid in the α-(AlxGa1-x)2O3 system. However, Vegard's law for optical bandgaps, derived from different models, required an additional term to account for the bowing effect. At x = 0.71, the gaps were 7.74, 7.03, 7.26, and 7.34 eV as derived from the Tauc plots for the direct bandgap, indirect bandgap, Tauc-Lorentz model, and O'Leary-Johnson-Lim model, respectively. The two-chamber system provides reliable and effective control of the Al content in α-(AlxGa1-x)2O3 alloys and heterostructures.
  • ItemOpen Access
    Recent Advances in Thermochemical Conversion of Woody Biomass for Production of Green Hydrogen and CO2 Capture: A Review
    (Elsevier BV, 2023) Pang, Shusheng
    Hydrogen as a green energy carrier has attracted great interests world-wide for substitution of fossil fuels and for abatement of the climate change concerns. However, green hydrogen from renewable resources is less than 0.1% at present in the world hydrogen production and this is largely from water electrolysis which is beneficial only when renewable electricity is used. Hydrogen production from diverse renewable resources is desirable. This review presents recent advances in hydrogen production from woody biomass through biomass steam gasification, producer gas processing and H2/CO2 separation. The producer gas processing includes steam-methane steam reforming (SMR) and water-gas shift (WGS) reactions to convert CH4 and CO in the producer gas to H2 and CO2. The H2 storage is also discussed using liquid carrier through hydrogenation are also discussed. The CO2 capture prior to the SMR is investigated to enhance H2 yield in the SMR and the WGS reactions.
  • ItemOpen Access
    Ensemble-Based Gradient Inference for Particle Methods in Optimization and Sampling
    (2023) Schillings , Claudia; Totzeck , Claudia; Wacker, Philipp
    We propose an approach based on function evaluations and Bayesian inference to extract higher-order differential information of objective functions from a given ensemble of particles. Pointwise evaluation of some potential V in an ensemble contains implicit information about first or higher order derivatives, which can be made explicit with little computational effort (ensemble-based gradient inference – EGI). We suggest to use this information for the improvement of established ensemble-based numerical methods for optimization and sampling such as Consensus-based optimization and Langevin-based samplers. Numerical studies indicate that the augmented algorithms are often superior to their gradient-free variants, in particular the augmented methods help the ensembles to escape their initial domain, to explore multimodal, non-Gaussian settings and to speed up the collapse at the end of optimization dynamics. The code for the numerical examples in this manuscript can be found in the paper’s Github repository
  • ItemOpen Access
    Quantitative Examination of the Anatomy of the Juvenile Sugar Maple Xylem
    (Public Library of Science (PLoS), 2023) Driller, Tenaya; Robinson, James; Clearwater M; Holland, Daniel; Van den Berg A; Watson, Matthew; Pereira FJ
    New methodologies have enabled viable sap yields from juvenile sugar maple trees. To further improve yields, a better understanding of sap exudation is required. To achieve this, the anatomy of the xylem must first be fully characterised. We examine juvenile maple saplings using light optical microscopy (LOM) and scanning electron microscopy (SEM), looking at sections cut along differing orientations as well as macerations. From this we measure various cell parameters. We find diameter and length of vessel elements to be 28 ± 8 μm and 200 ± 50 μm, for fibre cells 8 ± 3 μm and 400 ± 100 μm, and for ray parenchyma cells 8 ± 2 μm and 50 ± 20 μm. We also examine pitting present on different cell types. On vessel elements we observe elliptical bordered pits connecting to other vessel elements (with major axis of 2.1 ± 0.7 μm and minor 1.3 ± 0.3 μm) and pits connecting to ray parenchyma (with major axis of 4 ± 2 μm and minor 2.0 ± 0.7 μm). We observe two distinct pit sizes on fibres with circular pits 0.7 ± 0.2 μm in diameter and ellipsoidal pits 1.6 ± 0.4 μm by 1.0 ± 0.3 μm. We do not observe distinct pitting patterns on different fibre types. The various cell and pit measurements obtained generally agree with the limited data available for mature trees, with the exception of vessel element and fibre length, both of which were significantly smaller than reported values.
  • ItemOpen Access
    Driving change: Electric vehicle charging behavior and peak loading
    (Elsevier BV, 2024) Williams B; Bishop, Daniel; Hooper G; Chase, Geoff
    Electric vehicles (EVs) are projected to comprise 40 % of Aotearoa New Zealand's light vehicle fleet by 2040. However, charging decisions made by EV drivers, such as whether to charge immediately or delay charging, will affect peak electricity demand and lifetime of distribution network components. This study uses an agent-based model (ABM) of EV charging to investigate the effect of different EV penetration levels and owner charging decisions on components in New Zealand's residential electricity networks, although the methodology is wholly generalizable to other countries or regions. Monte Carlo simulation is performed for EV charging in a neighborhood of 71 houses, based on a representative residential distribution network, and simulated for 20 days. The key outcome measure is the rate of ‘Exceedance’ of the 300 kVA baseline transformer limit, where greater Exceedance entails shorter lifecycle and increased maintenance or capital costs to the provider. Results show delayed-charging algorithms (‘Altruistic charging’) decrease peak electricity demand and Exceedance, while drivers charging immediately (‘Selfish charging’) increases Exceedance. New Zealand's residential electricity networks are expected to accommodate a 40 % EV transition with 100 % Altruistic charging, as Exceedance is expected to increase less than 20 % from Exceedance without EVs. However, Selfish charging increases the rate of Exceedance by more than 250 %. Longer-term, increasing EV penetration and household electricity demand will require increased workplace charging infrastructure, electricity network upgrades, and/or automated and Internet of Things (IoT)-enabled Demand Side Management (DSM) of EV charging to avoid high rates of Exceedance and increased maintenance and replacement costs.
  • ItemOpen Access
    Zinc tin oxide metal semiconductor field effect transistors and their improvement under negative bias (illumination) temperature stress
    (AIP Publishing, 2017) Dang, Giang; Kawaharamura T; Furuta M; Allen, Martin
    © 2017 Author(s). Metal-semiconductor-field-effect-transistors (MESFETs) with silver oxide Schottky gates on zinc tin oxide (ZTO) channels showed fundamental differences in stability compared to conventional amorphous-oxide semiconductor thin-film-transistors (AOS-TFTs). The most severe negative-bias-temperature and negative-bias-illumination-temperature stress conditions, which usually degrade the performance of AOS-TFTs, significantly improved the switching characteristic of these ZTO MESFETs, producing devices with on:off current ratios, mobilities, and subthreshold swings of 8 × 106, 12 cm2 V−1 s−1, and 180 mV/dec, respectively. Further analysis confirmed that both negative bias and temperature (65 °C) were simultaneously required to produce this permanent effect that was linked to the electromigration of ionized donors from the MESFET depletion-region.
  • ItemOpen Access
    Interval analysis-based Bi-iterative algorithm for robust TDOA-FDOA moving source localisation
    (SAGE Publications, 2021) Qin N; Wang C; Shan C; Yang, Le
    In this study, an interval extension method of a bi-iterative is proposed to determine a moving source. This method is developed by utilising the time difference of arrival and frequency difference of arrival measurements of a signals received from several receivers. Unlike the standard Gaussian noise model, the time difference of arrival - frequency difference of arrival measurements are obtained by interval enclosing, which avoids convergence and initialisation problems in the conventional Taylor-series method. Using the bi-iterative strategy, the algorithm can alternately calculate the position and velocity of the moving source in interval vector form. Simulation results indicate that the proposed scheme significantly outperforms other methods, and approaches the Cramer-Rao lower bound at a sufficiently high noise level before the threshold effect occurs. Moreover, the interval widths of the results provide the confidence degree of the estimate.
  • ItemOpen Access
    Conductive Si-doped α-(AlxGa1−x)2O3 thin films with the bandgaps up to 6.22 eV
    (AIP Publishing, 2020) Dang, Giang; Tagashira Y; Yasuoka T; Liu L; Kawaharamura T
    This study systematically investigates the properties of (i) conductive Si-doped α-(AlxGa1−x)2O3 thin films grown via a third generation mist chemical vapor deposition system and (ii) Schottky diodes (SDs) and metal semiconductor field-effect transistors (MESFETs) fabricated on them. The use of chloro(3-cyanopropyl)dimethylsilane as the Si dopant resulted in conductive thin films in a wide range of Al contents x from 0 to 0.3. The resistivity fluctuated in the range from 0.14 Ω cm to 0.35 Ω cm at x ≤ 0.05 and abruptly increased as x exceeded 0.05. Nevertheless, a resistivity of 1.2 kΩ cm was measurable in an (Al0.3Ga0.7)2O3 film, whose bandgap of 6.22 eV was comparable to that of AlN. All the silver oxide SDs fabricated on these films functioned properly with the rectification ratios up to 105, while the MESFETs showed clear field-effect even in the α-(Al0.3Ga0.7)2O3 film. Interestingly, a linear dependence of barrier heights on ideality factors was obtained in diodes formed between the source and gate electrodes of these transistors despite the differences in the bandgaps. This plot yielded the average or “homogeneous” barrier height of ∼2.0 eV, suggesting that the Fermi level on the AgOy/Si:α-(AlxGa1−x)2O3 interface was pinned at ∼Ec −2.0 eV regardless of the Al content x.
  • ItemOpen Access
    The contribution of wet deposition and particulate matter to total copper, lead and zinc in stormwater runoff
    (2016) Murphy LU; Cochrane, Thomas; O'Sullivan, Aisling Dominique
    Wet deposition is an important process in the removal of heavy metal particulates from the atmosphere. However, the contribution of wet deposition to the total heavy metal deposition flux can vary widely between different airsheds. Understanding the contribution of wet deposition to the total metal deposition flux is important for accurate knowledge of local atmospheric deposition processes, which will subsequently help in the selection of appropriate stormwater treatment and management options. This research monitored Cu, Zn and Pb loads in wet deposition samples and in bulk deposition samples from modular concrete paving slab systems. In conjunction, ambient particulate matter (PM) concentrations were monitored to determine their contribution to the wet deposition flux. All research was conducted in an industrial land-use area in Christchurch, New Zealand. Results showed that wet deposition efficiently removed PM from the atmosphere, but after 1–2.5 antecedent dry days, PM concentrations recovered. Subsequent antecedent dry days, i.e > 1–2.5 d, did not influence PM concentrations. Pb loads in wet deposition were dependent on coarse PM (size range between 2.5 μm and 10 μm) concentrations. This suggested that there was a local source emitting coarse Pb particles into the atmosphere. Wet deposition was an important contributor of dissolved Zn to bulk deposition. However, dry deposition was the greatest source of total Cu, Zn, and Pb loads in bulk deposition. This is principally due to the low annual rainfall in Christ church, which limits pollutant removal via wet deposition unlike dry deposition, which is continually occurring.
  • ItemOpen Access
    Economic potential of essential oil production from New Zealand-grown Eucalyptus bosistoana
    (2023) Rajapaksha , Chamira; Greaves , Paul; Altaner, Clemens
    Farm foresters and other growers are establishing a ground-durable hardwood resource, including the emerging plantation species Eucalyptus bosistoana in New Zealand. The foliage of this species contains essential oils in quantity and quality suitable for commercial extraction. Essential oil production could improve the economic viability of E. bosistoana plantations, diversifying the grower’s income and providing an early revenue stream. This study assessed the economic potential for essential oil production from New Zealand grown E. bosistoana plantations. A sensitivity analysis indicated that uncertainty of leaf biomass availability, genetic as well as seasonal changes in oil content, and fuctuations in essential oil price are equally important on the viability of an essential oil operation. Small-scale essential oil production could be sustainably supplied with foliage from thinning and pruning operations sourced from the envisaged regional planting programmes and commence in 3–5 years. A large-scale operation could be supplied when trees will be harvested. Lastly, based on the operational costs of a domestic small-scale essential oil producer, oil value from E. bosistoana would exceed the cost of production.
  • ItemOpen Access
    A Biologically Constrained Cerebellar Model with Reinforcement Learning for Robotic Limb Control
    (Institute of Electrical and Electronics Engineers (IEEE), 2020) Liu , Rong; Zhang, Qi; Chen , Yaru; Wang , Jiaxing; Yang, Le
    The cerebellum is known to be critical for accurate adaptive control and motor learning. It has long been recognized that the cerebellum acts as a supervised learning machine. However, recent evidence shows that cerebellum is integral to reinforcement learning. This paper proposes a biologically plausible cerebellar model with reinforcement learning based on the cerebellar neural circuitry to eliminate the need for explicit teacher signals. The learning capacity of cerebellar reinforcement learning is first demonstrated by constructing a simulated cerebellar neural network agent and a detailed model of the human arm and muscle system in the Emergent virtual environment. Next, the cerebellar model is incorporated in both a simulated arm and a Geomagic Touch device to further verify the effectiveness of the cerebellar model in reaching tasks. Results from these experiments indicate that the cerebellar simulation is capable of driving the 'arm plant' to arrive at the target positions accurately. Moreover, by examining the effect of the number of basic units, we find the results are consistent with previous findings that the central nervous system may recruit the muscle synergies to realize motor control. The study described here prompts several hypotheses about the relationship between motor control and learning and may be useful in the development of general-purpose motor learning systems for machines.
  • ItemOpen Access
    α-(AlxGa1−x)2O3 single-layer and heterostructure buffers for the growth of conductive Sn-doped α-Ga2O3 thin films via mist chemical vapor deposition
    (AIP Publishing, 2020) Dang, Giang; Sato S; Tagashira Y; Yasuoka T; Liu L; Kawaharamura T
    A third generation mist chemical vapor deposition (3rd G mist CVD) system was used to grow six single-layer and two heterostructure α-(AlxGa1−x)2O3 buffers on c-plane sapphire substrates for the subsequent deposition of conductive Sn-doped α-Ga2O3 (Sn:α-Ga2O3) thin films. In the six single-layer buffers, the Al contents x increased from 0 to 0.66. The two heterostructure buffers consisted of six ∼20-nm- and ∼100-nm-thick layers laying on top of each other. The 3rd G mist CVD system enabled the growth of these complicated multi-layer heterostructures in a single run, while mono-crystallinity was still maintained in all grown layers. Strain was observed in the 20-nm heterostructure, while the layers in the 100-nm heterostructure almost fully relaxed and the Vegard’s law was followed even when the α-(AlxGa1−x)2O3 layers were stacked on each other. Transmission electron microscopy analyses show that the dislocation densities remained high in the order of 1010 cm−2 despite the employment of the buffers. PtOx and AgOx Schottky diodes (SDs) were fabricated on the Sn:α-Ga2O3 films. The barrier height vs ideality factor plots could be fitted by linear dependences, indicating that the large ideality factors observed in α-Ga2O3 SDs could be explained by the inhomogeneity of the SDs. The extrapolation of the dependences for the PtOx and AgOx SDs yielded homogeneous Schottky barrier heights of ∼1.60 eV and 1.62 eV, respectively, suggesting that the Fermi level was pinned at the Ec − 1.6 eV level. The Sn:α-Ga2O3 film grown on the strained 20-nm heterostructure buffer showed best characteristics overall.
  • ItemOpen Access
    Training mental imagery skills of elite athletes in virtual reality
    (2023) Wu Y; Lukosch, Stephan; Lukosch H; Lindeman R; McKee R; Fukuden S; Ross C; Collins D
    Mental imagery practice is widely used to help athletes prepare for competitions, as it can produce motor actions that enhance performance. The goal of imagery training for athletes is to create realistic images in their minds and to familiarize them with certain procedures, environments, and other aspects related to competition. Traditional imagery training methods use still images or videos, and athletes study the pictures or watch the videos in order to mentally rehearse. However, factors such as distractions and low realism can affect the training quality. In this paper, we present a Virtual Reality (VR) solution and a study that explores our hypotheses that H1: high-fidelity VR systems improve mental imagery skills, that H2: the presence of elements such as virtual onlookers or photographers in the VR environment arouse stronger emotional reactions and affect, and that H3: the presence of elements such as onlookers or photographers in the VR environment results in better mental imagery skill improvement. For that purpose, seven elite snow sports athletes were exposed to three training methods, Video, VR-Empty, and VR-Crowded. Our results show that a VR simulation with virtual onlookers (VR-Crowded) can significantly increase heart rate, which can induce increased emotional arousal. The results from validated questionnaires show no significant difference for the three training methods in terms of mental imagery and affect, but the results show an ascending trend for the athlete’s arousal from Video to the VR-Crowded condition. Gaze detection heat maps of interest areas for the two VR conditions support hypothesis H2 that environmental factors such as the presence of photographers, staff, and onlookers can increase head and eye movement, possibly indicating an increase in emotional arousal during imagery training. According to verbal feedback and interviews, athletes are more likely to use innovative training methods (e.g., the high-fidelity VR method) than traditional video-training methods
  • ItemOpen Access
    Multiple Initial Point Approach to Solving Power Flows for Monte Carlo Studies
    (MDPI AG, 2022) Schipper, Josh; McNab, Sharee; Kueh , Yuyin; Mukhedkar, Radnya
    Power flow solvers typically start from an initial point of power injection. This paper constructs a system of multiple initial points (SMIP) to enable selection of an appropriate initial point, with the objective to achieve a balanced improvement in the solution speed and accuracy, for problems with a large number of power flows. The intent is to recover time cost of forming the SMIP through the improvements to each power flow. The SMIP is tested on a time series based Monte Carlo study of Electric Vehicle (EV) hosting capacity in a low voltage distribution network, which has 5.4 million power flows. SMIP is applied to two power flow solvers: a Taylor series approximation and a Z-bus method. The accuracy of the quadratic Taylor series approximation was improved by a factor of 30 with a 27% increase in the solve time when compared against a single no-load initial point. A Z-bus solver with SMIP, limited to two iterations, gave the best performance for the EV hosting capacity case study.
  • ItemOpen Access
    Improving Neural Network classification of native forest in New Zealand with phenological features
    (Informa UK Limited, 2023) Ye, Ning; morgenroth, justin; Xu, Cong
    Changes in Vegetation Indices (VIs) over time can describe vegetation phenology; however, it is not known which phenological features contribute most to land cover classification. Feature selection could potentially solve this problem. In this study, phenological feature importance and selection were evaluated by using two-year Sentinel-2 (S-2) data and single-date PlanetScope (PS) to classify a 50 km2 native podocarp forest in New Zealand. The study area was classified into nine classes. Single-date PS and S-2 data were fused to a base image with the same spatial resolution as PS and 8 bands containing spectral data from S-2; this image was used to produce 30 Vegetation Indices (VIs). Phenological features–amplitude (AMP) and phase (PH) were extracted from these VIs using time-series S-2 only, and harmonic analysis in Google Earth Engine. For accurately classifying forests and identifying the most important features, three classification scenarios (fused bands & VIs, fused bands & phenological features, fused bands & VIs & phenological features) were developed using a Neural Network. Variable Selection Using Random Forest (VSURF) was applied on these scenarios to evaluate the impact of feature selection. Results indicate that VSURF could reduce the time needed for the classification while maintaining a comparable level of accuracy. Phenological features improved accuracy from 90% to 94%, driven mostly by Red-Edge Triangulated Vegetation Index-AMP&PH, Normalised Near-Infrared-PH, Greenness Index-PH, Water Body Index-PH, Normalised Difference Vegetation Index-PH, Normalised Green-PH, Red-Edge Normalised Difference Vegetation Index-PH, Leaf Chlorophyll Content-AMP, and Simple Near-Infrared and Blue Ratio-PH. These features reflect changes in the structure, biochemical, and physiological characteristics of the canopy. A lack of ground-based measurements precluded an evaluation of the accuracy of these phenological aspects and an explanation of their distinctive contribution to the model. Overall, the findings show that specific phenological features can improve the classification of New Zealand’s indigenous podocarp forests.
  • ItemOpen Access
    Influence of fuel structure on gorse fire behaviour
    (CSIRO Publishing, 2023) Valencia Correa, Andres; Melnik , Katherine O.; Sanders , Nick; Sew Hoy , Adam; Yan , Mozhi; Katurji, Marwan; Zhang, Jiawei; Schumacher, Benjamin; Hartley , Robin; Aguilar-Arguello , Samuel; Pearce , H. Grant; Finney , Mark A.; Clifford , Veronica; Strand , Tara
    Background. Complex interactions between fuel structure and fire substantially affect fire spread and spatial variability in fire behaviour. Heterogeneous arrangement of the fuel coupled with variability in fuel characteristics can impact heat transfer efficiency, preheating of unburned fuel and consequent ignition and spread. Aim. Study the influence of pre-burn fuel structure (canopy height, spatial arrangement) on fire behaviour (rate of spread, flame residence time) derived from high-resolution video of a prescribed gorse fire. Method. Rate of spread and flame residence time are calculated and mapped from high-resolution overhead visible-spectrum video, and compared with the Canopy Height Model derived from pre-burn Light Detection and Ranging (Lidar) scans. Results. Geospatial analytics can provide precision observations of fire behaviour metrics. Rates of spread under high wind conditions are influenced by local changes in canopy height and may be more dependent on other fuel characteristics, while flame residence time is better correlated with canopy height. Conclusions. These observational technology and spatio-temporal analytical techniques highlight how detailed fire behaviour characteristics can be derived from these data. Implications. The results have implications for wildfire modelling and Wildland–Urban Interface (WUI) building design engineers, as the reported dataset is suitable for model validation and the analysis contributes to further understanding of gorse fire hazard.
  • ItemOpen Access
    Nutrient treatment of greywater in green wall systems: A critical review of removal mechanisms, performance efficiencies and system design parameters.
    (Elsevier BV, 2023) Gholami , Moeen; O'Sullivan, Aisling Dominique; Mackey, Hamish
    Greywater has lower pathogen and nutrient levels than other mixed wastewaters, making it easier to treat and to reuse in nature-based wastewater treatment systems. Green walls (GWs) are one type of nature-based solutions (NBS) that are evolving in design to support on-site and low-cost greywater treatment. Greywater treatment in GWs involves interacting and complex physical, chemical, and biological processes. Design and operational considerations of such green technologies must facilitate these pivotal processes to achieve effective greywater treatment. This critical review comprehensively analyses the scientific literature on nutrient removal from greywater in GWs. It discusses nutrient removal efficiency in different GW types. Total nitrogen removal ranges from 7 to 91% in indirect green facades (IGF), 48–93% for modular living walls (MLW), and 8–26% for continuous living walls (CLW). Total phosphorus removal ranges from 7 to 67% for IGF and 2–53% for MLW. The review also discusses the specific nutrient removal mechanisms orchestrated by vegetation, substrates, and biofilms to understand their role in nitrogen and phosphorus removal within GWs. The effects of key GW design parameters on nutrient removal, including substrate characteristics, vegetation species, biodegradation, temperature, and operating parameters such as irrigation cycle and hydraulic loading rate, are assessed. Results show that greater substrate depth enhances nutrient removal efficiency in GWs by facilitating efficient filtration, straining, adsorption, and various biological processes at varying depths. Particle size and pore size are critical substrate characteristics in GWs. They can significantly impact the effectiveness of physicochemical and biological removal processes by providing sufficient pollutant contact time, active surface area, and by influencing saturation and redox conditions. Hydraulic loading rate (HLR) also impacts the contact time and redox conditions. An HLR between 50 and 60 mm/d during the vegetation growing season provides optimal nutrient removal. Furthermore, nutrient removal was higher when watering cycles were customized to specific vegetation types and their drought tolerances.
  • ItemOpen Access
    A versatile capillaric circuits microfluidic viscometer
    (2023) Meffan, Robert Claude; Menges , Julian; Mak , Daniel; Dolamore, Fabian; Fee , Conan; Nock, Volker; Dobson, Renwick C J
    A novel capillary-action microfluidic viscometer has been designed that can measure the relative viscosity of a sample compared to a control liquid. Using capillary action circuits, the viscosity of a sample is transformed into an easy-to-read comparative bargraph format while using no external instrumentation. This implementation is made practical through capillaric Field Effect Transistors, and the automated valving they enable. Using poly-ethylene glycol solutions as viscous samples, we demonstrate that the device can transduce the relative viscosity of a sample and control material consistently to within 2% in less than 5 minutes of measurement time. In addition, we show that the device can partially account for temperature through internal referencing. In the future, this device could be applied to medical care, quality assurance, and scientific measurements.
  • ItemOpen Access
    TDOA source positioning in the presence of outliers
    (Institution of Engineering and Technology (IET), 2019) Ma , Fuhe; Yang, Le; Zhang, Min; Guo , Fu-Cheng
    Source localisation using time difference of arrival (TDOA) measurements has drawn considerable attention in the past few decades. The presence of outliers in TDOAs could deteriorate the localisation performance significantly. Under the reasonable assumption that outliers are sparse and they do not dominate in the raw measurement set, a computationally efficient outlier-robust TDOA localisation method is proposed in this study. It integrates the half-quadratic minimisation and reweighted least absolute shrinkage and selection operator to iteratively identify the outliers and find the source location estimate using the TDOA inliers only. Both additive and multiplicative forms of the proposed method are established. Simulation results demonstrate the computational efficiency and effectiveness of the developed algorithms.