Engineering: Journal Articles

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Now showing 1 - 20 of 1819
  • ItemOpen Access
    An augmented lagrangian algorithm for recovery of ice thickness in unidirectional flow using the shallow ice approximation
    (Elsevier BV, 2022) McGeorge, Elizabeth; Moyers-Gonzalez M; Wilson, Phillip; Sellier, Mathieu
    A key parameter in ice flow modelling is basal slipping at the ice-bed interface as it can have a large effect on the resultant ice thickness. Unfortunately, its contribution to surface observations can be hard to distinguish from that of bed undulations. Therefore, inferring the ice thickness from surface measurements is an interesting and non-trivial inverse problem. This paper presents a method for recovering dually the ice thickness, in turn the bed topography, and the basal slip using only surface elevation and speed measurements. The unidirectional shallow ice approximation is first implemented to model steady state ice flow for given bedrock and basal slip profiles. This surface is then taken as synthetic observed data. To invert the data, an optimisation approach is taken, employing a basic Uzawa type algorithm to minimise the augmented Lagrangian objective functional. This optimisation recovers the diffusion coefficient which gives the best fit to observations. Combining this recovered diffusion with observed surface velocity, a simple Newton's method is used to recover both the ice thickness and basal slip. The method was successful in each test case and this implies that it should be possible to recover both of these parameters in two-dimensional cases also.
  • ItemOpen Access
    Topology Optimization and Numerical Validation for Heat Transfer Improvement in a Packed-Bed Reactor with Monolithic Catalyst
    (Elsevier BV, 2024) Erfani N; Symons, Digby; Fee, Conan; Watson, Matthew
    This study focuses on optimizing heat transfer in packed-bed reactors by simplifying the problem to a two-dimensional steady-state heat conduction scenario. The objective is to efficiently arrange a limited volume of high-conductivity material to transport heat from the source to the low-conductivity heat-absorbing materials, representing the reacting fluid phase. The topology optimization problem is tackled using a density-based method that relies on a gradient-based algorithm. The optimized design is extruded and compared to a honeycomb internal structure using high-fidelity simulations for steam methane reforming. Results show a 6.04% improvement in CH4 conversion for the optimized structure, highlighting the potential of this method to enhance monolithic catalysts, particularly in cases where heat transfer critically influences the reaction.
  • ItemOpen Access
    An electrical impedance tomography based artificial soft skin pressure sensor: Characterisation and force modelling
    (Elsevier BV, 2024) Ellingham R; Pretty, Christopher; Holder-Pearson L; Aw K; Giffney T
    Using electrical impedance tomography (EIT) to drive a pressure mapping device shows great potential, due to the customisability of the sensing domain and the non-invasive nature of the boundary electrodes. A pressure mapping system has been developed in this work that uses a carbon black silicone rubber (CBSR) nanoparticle sensing domain, giving the sensing domain a comparable softness to human skin tissue. To take this technology into a commercial application the performance of such an EIT-based sensor must be quantifiable and repeatable. In this work a series of experiments were repeated for various load locations, strains, and carbon black percentages. Capturing this data gave insight into the how the sensing domain performs over time and captured the transient events limiting the sensor. Metrics were determined to quantify the sensor’s spatial resolution. Load localisation could be determined with error values as low as 0.67 mm. A series of randomised test loads gave similar spatial performance results to the more structured experiments. A quasistatic conductance-force model of the material was developed with an accuracy of ± 0.78 N. One important metric is temporal resolution, as it is the least quantified performance metric in literature, however can be the most important for some applications. For the sensor domains tested, average settling times of between 19.0 – 44.5 s and 22.5 – 36.0 s were determined for 8 and 9 wt% CBSR samples. This sensor platform shows promise for future soft surface pressure mapping applications. Further use of the developed performance metrics will allow for a variety of sensor applications to be validated.
  • ItemOpen Access
    Nitrogen and Phosphorus Removal from Wastewater Using Calcareous Waste Shells—A Systematic Literature Review
    (2024) Wai K; O'Sullivan, Aisling Dominique; Bello Mendoza R
    Nitrogen and phosphorus in freshwaters are a global environmental challenge. Concurrently, the shellfish industry’s calcareous waste shells (CWSs) amount to ~10 million tonnes annually. CWSs can effectively adsorb dissolved pollutants, including nutrients, from water, which has motivated a growing number of experimental studies on recycling CWSs in wastewater treatment. This comprehensive literature review summarises and critically assesses the effectiveness of using different CWSs for removing nutrients from water. The effects of CWS type, initial pollutant concentration, adsorbent dosage, particle size, and contact time (CT) are investigated. The results show that phosphorus removal has been examined more than nitrogen. Most studies have been conducted using synthetic wastewater under laboratory conditions only. There is a large variability in experimental conditions, such as CWS adsorbent dosages (0.1–100 g/L) and CT (0.083–360 h). The calcination of CWSs is frequently used to enhance adsorption capacity. The Langmuir isotherm model has been found to fit adsorption data best when raw oyster shells are used, while the Freundlich isotherm is best when the adsorbent is calcinated mussel shells. The pseudo-second-order (PSO) kinetics model tends to describe adsorption data better than the pseudo-first-order (PFO) model in all shell types. There is significant potential for using calcareous waste shells to remove nutrients from wastewater in line with circular economy aspirations.
  • ItemOpen Access
    Sub-μm features patterned with laser interference lithography for the epitaxial lateral overgrowth of α-Ga₂O₃ via mist chemical vapor deposition
    (AIP Publishing, 2021) Dang, Giang; Yasuoka, T; Kawaharamura, T
    The low growth rate of mist chemical vapor deposition normally requires a long growth time to achieve coalescence in the epitaxial lateral overgrowth of α-Ga₂O₃ thin films on sapphire substrates. To address this issue, sub-μm features were patterned using laser interference lithography. Periodical stripes with a ∼590-nm pitch allowed the overgrowth of crack-free, void-free, and continuous thin films, while typical growth conditions using a low carrier gas flow rate and a low Ga precursor concentration were maintained. Coalescence was achieved even with a short growth time of <30 min and a low film thickness of <500 nm. Transmittance and x-ray diffraction spectra show that the film was predominantly in α-phase. Transmission electron microscopy (TEM) images reveal cup-top-like α-Ga₂O₃ regions of low dislocation density on the SiOx mask. Selected area electron diffraction and high-resolution TEM analyses confirm that an α-Ga₂O₃ layer was formed even on the top of the SiOx mask. Interestingly, the dislocations formed on the window areas did not bend toward the center of the masks; rather, a dislocation bending outward from the center was observed. This suggests the occurrence of early coalescence and/or atomic rearrangement.
  • ItemOpen Access
    A field-invariant method for quantitative analysis with benchtop NMR
    (Elsevier BV, 2019) Matviychuk, Yevgen; Yeo, J; Holland, Daniel
    Recently developed benchtop instruments have the potential of bringing the benefits of NMR spectroscopy to the wide variety of industrial applications. Unfortunately, their low spectral resolution poses significant challenges for traditional quantification approach. Here we present a novel model-based method designed to overcome these challenges. By defining our models in terms of quantum mechanical properties of the underlying spin system, we make our approach invariant to the spectrometer field strength and especially suitable for analyzing benchtop data. Our experimental results on prepared samples and natural fruit juices confirm the applicability of our method for quantitative analysis of medium-field 1H NMR spectra. The developed method succeeds in accurately separating the spectra of glucose anomers and even monitoring their interconversion in non-deuterated water. Furthermore, the compositions of unbuffered natural fruit juices estimated using data from 43 MHz to 400 MHz spectrometers are in good agreement with each other and with the reference values from nutrition databases.
  • ItemOpen Access
    Limitations of risk approaches
    (Informa UK Limited, 2019) Elms, David
    Risk methods are powerful and versatile, but they have limitations and subtle traps. The paper explores the nature of risk. There are three main difficulties. First, there is a problem with quality and completeness of information. Lack of precise information means that likelihood and consequences have to be estimated, so the information is vulnerable to biases: some are explored. Secondly, there is a serious problem of completeness in risk models, where omissions can lead to serious consequences. Unexpected events, sometimes called ‘black swans’, abound. Thirdly, the conjunction of very small probabilities and major consequences can lead to unreliable and dubious results. Applications areas considered are structural engineering, project management and risk management generally. There are situations where a resilience approach is preferable to risk.
  • ItemOpen Access
    Discussion on ‘A framework for a civil engineering systems BOK’ by David Carmichael
    (Informa UK Limited, 2021) Elms, David
    Carmichael’s paper offers a framework for civil engineering systems work. The approach is rigorous. But equally rigorous should be the principles underlying the work, including a clear and unambiguous defining purpose and a careful attention to modelling principles. That is, a rigorous process is just as important as a rigorous framework. Suggested additions to the proposed framework are: purpose, information (including uncertainty and quality), modelling, topology and value.
  • ItemOpen Access
    Risk and its risks: discussion of ‘Risk–a commentary’ by D.G. Carmichael
    (Informa UK Limited, 2017) Elms, David
    The nature of risk needs to be more clearly understood. Risk management could be tightened as a discipline, particularly by adopting an underlying foundation of systems thinking. Risk management, even when well done, has inherent limitations, and these should be well understood, particularly those arising from modelling, completeness, correlation effects, and the often-great uncertainties in estimates of both likelihood and consequence. Modelling is centrally important: both this and risk must be intimately related to decision-making. A clear understanding of this connection is essential to sound work in the discipline.
  • ItemOpen Access
    Improving community resilience to natural events
    (TAYLOR & FRANCIS LTD, 2015) Elms, David
    Improving community resilience requires a way of thinking about the nature of a community. Two complementary aspects are proposed: the flows connecting the community with its surrounding environment and the resources the community needs for its ongoing life. The body of necessary resources is complex, with many interactions between its elements. A systems approach is required to understand the issues adequately. Community resilience is discussed in general terms together with strategies for improving it. The ideas are then illustrated and amplified by an extended case study addressing means of improving the resilience of a community on the West Coast of New Zealand to natural disasters. The case study is in two phases. The first relies on a mix of on-the-ground observations and constructed scenarios to provide recommendations for enhancing community resilience, while the second complements the first by developing a set of general lessons and issues to be addressed from observations of the Christchurch earthquakes of 2010 and 2011.
  • ItemOpen Access
    The systems stance
    (Informa UK Limited, 2020) Elms, David
    An engineer can be greatly helped in dealing with complex and unusual systems by taking a specific attitude to the world of reality: The Systems Stance. It involves an attitude of personal engagement and in which one relates to almost all reality by means of models. Of the many forms of model, the most important distinction is between generic and specific models. Modelling is discussed generally including the discipline required by a set of system modelling principles. A more detailed discussion on systems and systems models follows, where model definition is seen as a process marked by increasing confidence or decreasing uncertainty. The advantages and limitations of subjective approaches are stressed, together with a need for care and a sound ethical foundation. Specific areas of interest are: the place of temporal issues; questions of value emphasising quality and a system aesthetic; and the relation of the systems stance to uncertainty and surprise.
  • ItemOpen Access
    Avoiding apocalypse: clarity and collaboration
    (Informa UK Limited, 2022) Elms, David
    The world faces grave problems stemming from environmental issues, but apocalyptic disaster is not inevitable. The problems arise primarily from human failure to understand the issues and act collectively to deal with them. Any solution must therefore address human factors. This paper considers two: a lack of clarity in thought, aims and action, and the destructive nature of unconstrained conflict at all levels, particularly between groups of all sizes. The first can be helped by the discipline of systems engineering which aims to achieve clarity in complex situations, and the second can use the clarity of understanding to help groups interact while having an attitude of both collaboration and competition. Means of achieving clarity are discussed. Examples demonstrate how clarity has cut through difficult problems and also, in some detail, how, in a major project management situation, a clear-thinking approach brought normally competing groups to work together in such a way that they had to simultaneously collaborate and compete to the delight of the clients and the mutual benefit of all. It can be done and catastrophe avoided.
  • ItemOpen Access
    Application of travelling behaviour models for thermal responses in large compartment fires
    (Elsevier BV, 2022) Nan, Z; Khan, Aatif Ali; Jiang, L; Chen, S; Usmani, A
    Large open-plan compartment fires in modern buildings may exhibit a local burning region travelling across the floor plan as a ‘travelling fire’. This phenomenon has been found in the forensic investigations of fire accidents and in the large compartment fire tests. The fire impact in a large compartment is spatially non-uniform and time-variant, which can cause severe local damage to structural components. Advanced from the previous models assuming constant travelling, the natural fire model established in this paper comprises time-variant and test-based travelling behaviour models and localised fire models of various modes. It is demonstrated with the fast-spread Veselí fire test and the slow-spread Malveira fire test. A generic structural model is set up within OpenSees for fire to examine the thermal impact on structural members under various travelling fire scenarios of different travelling parameters, fire travelling directions, and beam sizes. Locally much higher thermal responses are represented after introducing behaviour models while adopting the same design fire load. Based on the work in this paper, a library of design fire models can be potentially enabled to examine the fire safety performance of structures regarding the realistic fire load and fire impact aiming for discovering unknown worse fire scenarios.
  • ItemOpen Access
    Facade Fire Hazards of Bench-Scale Aluminum Composite Panel with Flame-Retardant Core
    (Springer Science and Business Media LLC, 2023) Khan, Aatif Ali; Lin S; Huang X; Usmani, A
    Façade fires in tall buildings are currently occurring more than once a month globally that are responsible for many casualties and billions of dollars in losses. In particular, the tragic Grenfell Tower fire in London with more than 70 fatalities raised the profile of façade fire hazard. This work used well-controlled irradiation up to 60 kW/m2 to re-assess the fire hazard of typical flame-retardant aluminum composite panels (ACPs) with a dimension of 10 cm × 10 cm × 0.5 cm. We found that the vertically oriented ACPs with the “non-combustible” A2-grade and “limited-combustible” B-grade cores could still be ignited above 35 kW/m2 and 25 kW/m2, after the front aluminum layer peeled off. The peak heat release rate per unit area of these ACPs could be higher than common materials like timber and PVC. Moreover, compared to the B-core panel, the A2-core panel showed a greater fire hazard in terms of a shorter ignition delay time, a higher possibility of the core peel-off, and a longer flaming duration under current test size and fixing condition. Because the ACP is a complex system, its fire hazard is not simply controlled by the core material. The structural failure of ACP in fire, including peel-off, bending, softening and cracking, may further increase the fire hazard depending on the scale effect, boundary and fixing conditions. This research improves our understanding of the systematic fire behaviors of façade panels and helps rethink the fire risk and test methods of the building façade. Graphical Abstract: [Figure not available: see fulltext.].
  • ItemOpen Access
    Model characterisation of localised burning impact from localised fire tests to travelling fire scenarios
    (Elsevier BV, 2022) Khan, Aatif Ali; Nan, Z; Jiang, L; Gupta, V; Chen S; Khan, MA; Hidalgo, J; Usmani, A
    Fire safety of modern buildings is crucial and the fire safety design of these buildings has been a challenging task. Large open-plan compartments are commonly designed in modern urbanisation and the fire behaviour in such compartments is different from the traditional knowledge built upon small compartment fire research. Various experimental studies have been performed to represent such fires to evaluate the structural fire resistance, which were accompanied by a series of travelling fire models to describe the non-uniform fire impact in large compartments. However, the localised fire models adopted in the latest travelling fire methodology were derived from localised fire tests of unconfined ceiling boundaries. The effects of smoke generation due to fire during various stages of the fire development are not included explicitly. This paper characterises the thermal impact on structural members from the localised fire tests and extends the simulation models and analysis approaches to localised fires in large compartments. Comparing the cases with soffits and without soffits, temperature differences of up to 150 °C are observed and the convective coefficient adopted as 35 W/m2K is too high. The work recommends to modify the current localised fire models to consider realistic fire sizes and smoke layer with the recognition of semi-confined conditions in large compartment fire scenarios. By including these aspects, it is possible to establish more universal design fire models to overcome the current limitations and to address the fire impact in compartments of various sizes and ventilation conditions.
  • ItemOpen Access
    Response of restrained stainless steel corrugated web beams at elevated temperature
    (Elsevier BV, 2022) Khan, MA; Khan, Aatif Ali; Cashell, KA; Usmani, A
    This paper is focused on the fire behaviour of axially restrained corrugated web beams made from stainless steel. A finite element (FE) model is developed and validated against available fire test results on restrained flat web carbon steel beams, unrestrained stainless steel cellular beams and numerical studies conducted on carbon steel corrugated web beams in fire. The verified FE model is then employed to conduct an extensive parametric study to assess the relative influence of key properties on the response. The behaviour of stainless steel corrugated web beams (SSCWBs) is compared to that of stainless steel flat web beams (SSFWBs) during exposure to a standard fire under axially restrained support conditions. The axial compression developed in an SSCWB is shown to be significantly lower than that of a comparable SSFWB due to the reduced axial stiffness. A number of parameters are examined including the grade of steel, load ratio, presence of axial restraint as well as thicknesses of the flange and web. It is shown that the overall behaviour of SSCWBs is quite similar compared with equivalent carbon steel corrugated web beams (CSCWBs). However, the stainless steel beams also show much improved performance in terms of survival time due to better retention of mechanical properties at elevated temperature compared with carbon steel. An analytical model for predicting the critical parameters related to the axial force-temperature response of SSCWBs is also presented and verified against the results obtained from the FE models.
  • ItemOpen Access
    ExtSpecR: An R Package and Tool for Extracting Tree Spectra from UAV-Based Remote Sensing
    (American Association for the Advancement of Science (AAAS), 2023) Liu, Z; Al-Sarayreh, M; Xu, Cong; Tomasetto, F; Li, Y
    The development of unmanned aerial vehicle (UAV) remote sensing has been increasingly applied in forestry for high-throughput and rapid acquisition of tree phenomics traits for various research areas. However, the detection of individual trees and the extraction of their spectral data remain a challenge, often requiring manual annotation. Although several software-based solutions have been developed, they are far from being widely adopted. This paper presents ExtSpecR, an open-source tool for spectral extraction of a single tree in forestry with an easy-to-use interactive web application. ExtSpecR reduces the time required for single tree detection and annotation and simplifies the entire process of spectral and spatial feature extraction from UAV-based imagery. In addition, ExtSpecR provides several functionalities with interactive dashboards that allow users to maximize the quality of information extracted from UAV data. ExtSpecR can promote the practical use of UAV remote sensing data among forest ecology and tree breeding researchers and help them to further understand the relationships between tree growth and its physiological traits.
  • ItemOpen Access
    Intuitive decisions and heuristics - an alternative rationality
    (Informa UK Limited, 2013) Elms, David; Brown CB
    Two ways of making a decision are objectively using formal analysis and subjectively using intuition. Psychological research has shown that the latter leads to better decisions in complex situations. Intuitive decision-making uses simplified rules of thumb heuristics. In engineering terms, complexity implies complex systems. A set of rules and principles - heuristics - is presented as a guide for making subjective decisions in complex system contexts, one aspect of which is to provide quality control and guard against bias and error. An extended practical example of the use of these heuristics is given involving assessment of the safety of nuclear-powered ships. © 2013 © 2013 Taylor & Francis.
  • ItemOpen Access
    Engineering decisions: Framework, process and concerns
    (Informa UK Limited, 2013) Brown CB; Elms, David
    Decisions are central to engineering processes and hold them together. It is argued that better decisions will lead to better engineering. To achieve better decisions requires that they be understood in detail. A typical decision is broken down into its essential requirements and processes, thus displaying the components of its framework. The process leads to the identification of a number of concerns. The components are discussed and a set of issues where more work needs to be done is identified. There are significant implications for both engineering practice and engineering education. © 2013 © 2013 Taylor & Francis.
  • ItemOpen Access
    Improving infrastructure resilience
    (Informa UK Limited, 2019) Elms, David; McCahon I; Dewhirst R
    Most formal engineering approaches to uncertainty use risk-based methods. Because risk formulations have a number of limitations there are situations where a resilience approach is preferable. A problem with resilience is the difficulty of measuring it. The paper discusses the issue and shows how a resilience formulation was used to prioritise actions to improve infrastructure resilience in an extensive region of New Zealand. The region was a complex system-of-systems so a systems approach was used. Once modelled, the infrastructure system was probed using three natural-hazard scenarios to determine system-element vulnerabilities. The vulnerability of each element was then matched with an importance value reflecting the effect of an element failure on community resilience. Community resilience was quantified in terms of overall income coming from three main sources each of which could be characterised by flow in a virtual pipeline. The pipelines were complex: tourism, for instance, required not only roads but also accommodation, communication, access and so on. The effect of infrastructure failures on pipeline flow and hence income quantified the relative importance of each infrastructure element. The vulnerability and importance values as a pair prioritised resilience-improving intervention for the element.