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  • Journal article
    Wang K, Xin G, Xin S, Mistry M, Vijayakumar S, Kormushev Pet al., 2023,

    A unified model with inertia shaping for highly dynamic jumps of legged robots

    , MECHATRONICS, Vol: 95, ISSN: 0957-4158
  • Conference paper
    Ballou N, Deterding S, 2023,

    ‘I Just Wanted to Get it Over and Done With’: a grounded theory of psychological need frustration in video games

    , CHI PLAY 2023, Publisher: Association for Computing Machinery (ACM), Pages: 217-236, ISSN: 2573-0142

    Psychological need frustration—experiences like failure, loneliness, or coercion—is emerging as a promising explanation for why people disengage with games and other entertainment media, and how media may induce dysregulated use and ill-being. However, existing research on game-related need frustration relies on general instruments with unclear content validity for games. We also do not know how need frustration arises in video games, nor how it leads to disengagement. We therefore conducted a semi-structured interview study with 12 video game players, following grounded theory methods to develop a model of need-frustrating play. We find that need frustration is a common and impactful experience in games, with distinct antecedents not fully captured in existing measures. Felt need frustration arises when observed need-frustrating events negatively violate expected need frustration or satisfaction; repeated violations update players’ expectations, which lead them to modulate or quit play to reduce expected frustration exposure.
  • Conference paper
    Deterding S, Cutting J, 2023,

    Objective difficulty-skill balance impacts perceived balance but not behaviour: a test of flow and self-determination theory predictions

    , CHI PLAY 2023, Publisher: Association for Computing Machinery (ACM), Pages: 1179-1205, ISSN: 2573-0142

    Flow and self-determination theory predict that game difficulty in balance with player skill maximises enjoy- ment and engagement, mediated by attentive absorption or competence. Yet recent evidence and methodologi- cal concerns are challenging this view, and key theoretical predictions have remained untested, importantly which objective difficulty-skill ratio is perceived as most balanced. To test these, we ran a preregistered study (n=309) using a Go-like 2-player game with an AI opponent, randomly assigning players to one of three objective difficulty-skill ratios (AI plays to win, draw, or lose) over five matches. The AI successfully ma- nipulated objective balance, with the draw condition perceived as most balanced. However, balance did not impact play behaviour, nor did we find the predicted uniform ‘inverted-U’ between balance and positive play experiences. Importantly, we found both theories too underspecified to severely test. We conclude that balance and competence likely matter less for behavioural engagement than commonly held. We propose alternative factors such as player appraisals, novelty, and progress, and debate the value and challenges of theory-testing work in games HCI.
  • Journal article
    Arteaga JM, Sanchez J, Elsakloul F, Marin M, Zesiger C, Pucci N, Norton GJ, Young DJ, Boyle D, Yeatman E, Hallett PD, Roundy S, Mitcheson PDet al., 2023,

    High frequency inductive power transfer through soil for agricultural applications

    , IEEE Transactions on Power Electronics, Vol: 38, Pages: 13415-13429, ISSN: 0885-8993

    This paper presents 13.56 MHz inductive powertransfer (IPT) through soil for sensors in agricultural ap-plications. Two IPT system designs and their prototypes are presented. The first was designed for gathering data and observing the relationship between the performance of the coil driving circuits in response to water content, salinity, organic matter and compaction of the soil. The second prototype was designed as an application demonstrator, featuring IPT to an in-house sensor node enclosure buried 200 mm under the surface of an agricultural field. The results highlight that from the parameters studied, the combination of high salinity and high water content significantly increases the losses of the IPT system.The experiments demonstrate an over 40% rise in the losses from dc source to dc load after a 16% increase in soil water content and high salinity. In the technology demonstrator we mounted an IPT transmitter on a drone to wirelessly power an in-house bank of supercapacitors in the buried sensor-node enclosure. A peak power transfer of 30 W received at over 40% efficiency was achieved from a 22 V power supply on the drone to the energy storage under the ground. The coil separation in these experiments was 250 mm of which 200 mm correspond to the layer of soil. The coupling factor in all the experiments was lower than 5%. This system was trialled in the field for forty days andwireless power was performed five times throughout.
  • Journal article
    Psarras S, Munoz R, Ghajari M, 2023,

    Compression performance of composite plates after multi-site impacts: A combined experimental and finite element study

    , COMPOSITE STRUCTURES, Vol: 322, ISSN: 0263-8223
  • Journal article
    Zhao Y, 2023,

    Ampere-hour-scale soft-package potassium-ion hybrid capacitors enabling 6-minute fast-charging

    , Nature Communications, Vol: 14, ISSN: 2041-1723

    Extreme fast charging of Ampere-hour (Ah)-scale electrochemical energy storage devices targeting charging times of less than 10 minutes are desired to increase widespread adoption. However, this metric is difficult to achieve in conventional Li-ion batteries due to their inherent reaction mechanism and safety hazards at high current densities. In this work, we report 1 Ah soft-package potassium-ion hybrid supercapacitors (PIHCs), which combine the merits of high-energy density of battery-type negative electrodes and high-power density of capacitor-type positive electrodes. The PIHC consists of a defect-rich, high specific surface area N-doped carbon nanotube-based positive electrode, MnO quantum dots inlaid spacing-expanded carbon nanotube-based negative electrode, carbonate-based non-aqueous electrolyte, and a binder- and current collector-free cell design. Through the optimization of the cell configuration, electrodes, and electrolyte, the full cells (1 Ah) exhibit a cell voltage up to 4.8 V, high full-cell level specific energy of 140 Wh kg−1 (based on the whole mass of device) with a full charge of 6 minutes. An 88% capacity retention after 200 cycles at 10 C (10 A) and a voltage retention of 99% at 25 ± 1 °C are also demonstrated.
  • Journal article
    Kallis C, Calvo R, Schuller B, Quint Jet al., 2023,

    Development of an asthma exacerbation risk prediction model for conversational use by adults in England

    , Pragmatic and Observational Research, Vol: 14, Pages: 111-125, ISSN: 1179-7266

    Background: Improving accurate risk assessment of asthma exacerbations, and reduction via relevant behaviour change among people with asthma could save lives and reduce health care costs. We developed a simple personalised risk prediction model for asthma exacerbations using factors collected in routine healthcare data for use in a risk modelling feature for automated conversational systems.Methods: We used pseudonymised primary care electronic healthcare records from the Clinical Practice Research Datalink (CPRD) Aurum database in England. We combined variables for prediction of asthma exacerbations using logistic regression including age, gender, ethnicity, Index of Multiple Deprivation, geographical region and clinical variables related to asthma events.Results: We included 1,203,741 patients divided into three cohorts to implement temporal validation: 898,763 (74.7%) in the training sample, 226,754 (18.8%) in the testing sample and 78,224 (6.5%) in the validation sample. The Area under the ROC curve (AUC) for the full model was 0.72 and for the restricted model was 0.71. Using a cut-off point of 0.1, approximately 27 asthma reviews by clinicians per 100 patients would be prevented compared with a strategy that all patients are regarded as high risk. Compared with patients without an exacerbation, patients who exacerbated were older, more likely to be female, prescribed more SABA and ICS in the preceding 12 months, have history of GORD, COPD, anxiety, depression, live in very deprived areas and have more severe disease.Conclusion: Using information available from routinely collected electronic healthcare record data, we developed a model that has moderate ability to separate patients who had an asthma exacerbation within 3 months from their index date from patients who did not. When comparing this model with a simplified model with variables that can easily be self-reported through a WhatsApp chatbot, we have shown that the predictive performance of the model is
  • Journal article
    Ferraro P, Yu JY, Ghosh R, Alam SE, Marecek J, Wirth F, Shorten Ret al., 2023,

    On unique ergodicity of coupled AIMD flows

    , INTERNATIONAL JOURNAL OF CONTROL, ISSN: 0020-7179
  • Journal article
    Lu X, Lian GJ, Ge R, Parker J, Sadan MK, Smith R, Cumming Det al., 2023,

    Microstructure of Conductive Binder Domain for Electrical Conduction in Next-Generation Lithium-Ion Batteries

    , Energy Technology, Vol: 11, ISSN: 2194-4288

    The purpose of this work is to investigate the structure and mechanism of long-range electronic contacts which are formed by wet mixing and their interaction and relationship with the structure responsible for ion transfer within the conductive binder domain of next-generation LiNi0.6Mn0.2Co0.2O2 lithium-ion batteries. This article introduces a novel concept involving an efficient adapted structure model, which includes a bridge structure with two “nested” small and large pore systems, and an effective electrode conduction mechanism involving two “nested” percolation systems. The article also highlights a limitation in the improvement of the battery performance by percolation systems for electron transfer, which is restricted by pore systems for ion transfer through the ratio of electrical conductivity (σ) and ionic conductivity (κ) as σ/κ = 10. The findings of this article may provide valuable insight for formulation design and manufacturing of an optimal structure of the conductive binder domain for next-generation lithium-ion batteries.
  • Journal article
    Qi N, Pinson P, Almassalkhi MR, Cheng L, Zhuang Yet al., 2023,

    Chance-constrained generic energy storage operations under decision-dependent uncertainty

    , IEEE Transactions on Sustainable Energy, Vol: 14, Pages: 2234-2248, ISSN: 1949-3029

    Compared with large-scale physical batteries, aggregated and coordinated generic energy storage (GES) resources provide low-cost, but uncertain, flexibility for power grid operations. While GES can be characterized by different types of uncertainty, the literature mostly focuses on decision-independent uncertainties (DIUs), such as exogenous stochastic disturbances caused by weather conditions. Instead, this manuscript focuses on newly-introduced decision-dependent uncertainties (DDUs) and considers an optimal GES dispatch that accounts for uncertain available state-of-charge (SoC) bounds that are affected by incentive signals and discomfort levels. To incorporate DDUs, we present a novel chance-constrained optimization (CCO) approach for the day-ahead economic dispatch of GES units. Two tractable methods are presented to solve the proposed CCO problem with DDUs: (i) a robust reformulation for general but incomplete distributions of DDUs, and (ii) an iterative algorithm for specific and known distributions of DDUs. Furthermore, reliability indices are introduced to verify the applicability of the proposed approach with respect to the reliability of the response of GES units. Simulation-based analysis shows that the proposed methods yield conservative, but credible, GES dispatch strategies and reduced penalty cost by incorporating DDUs in the constraints and leveraging data-driven parameter identification. This results in improved availability and performance of coordinated GES units.
  • Journal article
    Ruan H, Barreras JV, Steinhardt M, Jossen A, Offer GJ, Wu Bet al., 2023,

    The heating triangle: A quantitative review of self-heating methods for lithium-ion batteries at low temperatures

    , Journal of Power Sources, Vol: 581, Pages: 1-16, ISSN: 0378-7753

    Lithium-ion batteries at low temperatures have slow recharge times alongside reduced available power and energy. Battery heating is a viable way to address this issue, and self-heating techniques are appealing due to acceptable efficiency and speed. However, there are a lack of studies quantitatively comparing self-heating methods rather than qualitatively, because of the existence of many different batteries with varied heating parameters. In this work, we review the current state-of-the-art self-heating methods and propose the heating triangle as a new quantitative indicator for comparing self-heating methods, towards identifying/developing effective heating approaches. We define the heating triangle which considers three fundamental metrics: the specific heating rate (°C·g·J−1), coefficient of performance (COP) (−), and specific temperature difference (°C·hr), enabling a quantitative assessment of self-heating methods using data reported in the literature. Our analysis demonstrates that very similar metrics are observed for the same type of self-heating method, irrespective of the study case, supporting the universality of the proposed indicator. With the comparison insights, we identify research gaps and new avenues for developing advanced self-heating methods. This work demonstrates the value of the proposed heating triangle as a standardised approach to compare heating methods and drive innovation.
  • Conference paper
    Attar HR, Lei Z, Li N, 2023,

    Deep learning enabled tool compensation for addressing shape distortion in sheet metal stamping

    , 14th International Conference on the Technology of Plasticity, Publisher: Springer, Cham

    This paper presents a novel deep learning-based platform for addressing shape distortion in sheet metal stamping (e.g., springback, thermal distortion) by tool compensation. Conventional approaches to tool compensation involve computationally expensive Finite Element (FE) simulations to update tool geometries. In contrast, the proposed platform uses a generator network to create 3D tool geometries and an evaluator network to predict the resulting shape distortion and post-stamping thinning. The generated tool geometries are iteratively updated by a gradient-based optimisation technique in the direction of minimising shape distortion in the resulting component. The platform is demonstrated on a cold stamped U-channel component case study, which experiences severe shape distortion in the form of springback. The optimisation problem was formulated to find the optimum tool geometry that enables a desired U-channel geometry to be formed after springback by tool compensation, while meeting a maximum thinning constraint. The platform successfully optimised the tool geometry to compensate for springback in this setting, showcasing its effectiveness in improving manufacturing outcomes and product quality. The presented approach offers a superior method for addressing shape distortion in stamping processes, as compared to conventional FE simulation iterations or trial-and-error methods. This approach can efficiently and effectively compensate for arbitrarily complex tool geometries without requiring extensive process expertise.
  • Conference paper
    Hogg A, Liu H, Mads J, Picinali Let al., 2023,

    Exploring the Impact of Transfer Learning on GAN-Based HRTF Upsampling

    , EAA Forum Acusticum, European Congress on Acoustics
  • Journal article
    Tsaousoglou G, Giraldo JS, Pinson P, Paterakis NGet al., 2023,

    Fair and Scalable Electric Vehicle Charging Under Electrical Grid Constraints

    , IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS, ISSN: 1524-9050
  • Journal article
    Wang M, Yang K, Ji Y, Liao X, Zhang G, Masteghin MG, Peng N, Richheimer F, Li H, Wang J, Liu X, Yang S, Petrucco E, Shearing P, Castro FA, Silva SRP, Zhao Y, Pan F, Zhao Yet al., 2023,

    Developing highly reversible Li-CO<sub>2</sub> batteries: from on-chip exploration to practical application

    , ENERGY & ENVIRONMENTAL SCIENCE, Vol: 16, Pages: 3960-3967, ISSN: 1754-5692
  • Conference paper
    Meyer J, Picinali L, 2023,

    Comparison of simulated head-related transfer functions accuracy for different model complexities using the finite-difference time-domain method

    , Forum Acusticum 2023, Pages: 131-137, ISSN: 2221-3767

    The use of finite-difference time-domain (FDTD) simula-tions is relevant for several applications in virtual acous-tics. One of these is the numerical calculation of head-related transfer functions (HRTFs). This study investi-gates the effect of varying the geometrical complexity(shape, level of details) of a human head/torso model onthe calculation of its HRTFs using an FDTD solver. Inparticular, the interest is on the accuracy of the obtainedsimulation results with respect to the human head/torsomodel complexity. For that aim, a solution verificationprocess is undertaken, and a single sphere, a two-sphereand a human head and torso models are considered. Theresults indicate that relatively small 95% confidence in-tervals on the solution verification results are achieved,indicating relatively good accuracy for the prediction ofHRTFs up to relatively high frequencies for the single andtwo-sphere models considered. However, for the simpli-fied human head and torso model, a similar accuracy isachieved only up to a lower frequency.
  • Conference paper
    Giraud P, Sum K, Pontoppidan NH, Poole K, Picinali Let al., 2023,

    Adaptation to altered interaural time differences in a virtual reality environment

    , Forum Acusticum 2023

    Interaural time differences (ITDs) are important cues fordetermining the azimuth location of a sound source andneed to be accurately reproduced, in a virtual reality (VR)environment, to achieve a realistic sense of sound location for the listener. ITDs are usually included in headrelated transfer functions (HRTFs) used for audio rendering, and can be individualised to match the user’s headsize (e.g. longer ITDs are needed for larger head sizes).In recent years, studies have shown that it is possibleto train subjects to adapt and improve their performancein sound localisation skills to non-individualized HRTFs.The analysis of such improvements has focused mainlyon adaptation to monoaural spectral cues rather than binaural cues such as ITDs. In this work listeners are placedin a VR environment and are asked to localise the sourceof a noise burst in the horizontal plane. Using a genericnon-individualized HRTF with its ITD modified to matchthe head size of each participant, test and training phasesare alternated, with the latter providing continuous auditory feedback. The experiment is then repeated with ITDssimulating larger (150%) and smaller (50%) head sizes.Comparing localisation accuracy before and after training, it is observed that while training seems to improvesound localisation performance, this varies according tothe simulated head size and target location.
  • Conference paper
    Picinali L, Grimm G, Hioka Y, Kearney G, Johnston D, Jin C, Simon LSR, Wuthrich H, Mihocic M, Majdak P, Vickers Det al., 2023,

    VR/AR and hearing research: current examples and future challenges

    , Forum Acusticum 2023

    A well-known issue in clinical audiology and hearing research is the level of abstraction of traditional experimental assessments and methods, which lack ecological validity and differ significantly from real-life experiences,often resulting in unreliable outcomes. Attempts to dealwith this matter by, for example, performing experimentsin real-life contexts, can be problematic due to the difficulty of accurately identifying control-specific parametersand events. Virtual and augmented reality (VR/AR) havethe potential to provide dynamic and immersive audiovisual experiences that are at the same time realistic andhighly controllable. Several successful attempts have beenmade to create and validate VR-based implementationsof standard audiological and linguistic tests, as well asto design procedures and technologies to assess meaningful and ecologically-valid data. Similarly, new viewpoints on auditory perception have been provided by looking at hearing training and auditory sensory augmentation, aiming at improving perceptual skills in tasks suchas speech understanding and sound-source localisation. In this contribution, we bring together researchers active inthis domain. We briefly describe experiments they havedesigned, and jointly identify challenges that are still openand common approaches to tackle them
  • Conference paper
    Valzolgher C, Capra S, Pavani F, Picinali Let al., 2023,

    Training spatial hearing skills in virtual reality through a sound-reaching task

    , Forum Acusticum 2023

    Sound localization is crucial for interacting with thesurrounding world. This ability can be learned across timeand improved by multisensory and motor cues. In the lastdecade, studying the contributions of multisensory andmotor cues has been facilitated by the increased adoption ofvirtual reality (VR). In a recent study, sound localizationhad been trained through a task where the visual stimuliwere rendered through a VR headset, and the auditory onesthrough a loudspeaker moved around by the experimenter.Physically reaching to sound sources reduced soundlocalization errors faster and to a greater extent if comparedto naming sources’ positions. Interestingly, training efficacyextended also to hearing-impaired people. Yet, thisapproach is unfeasible for rehabilitation at home. Fullyvirtual approaches have been used to study spatial hearinglearning processes, performing headphones-renderedacoustic simulations. In the present study, we investigatewhether the effects of our reaching-based training can beobserved when taking advantage of such simulations,showing that the improvement is comparable between thefull-VR and blended VR conditions. This validates the useof training paradigms that are completely based on portableequipment and don’t require an external operator, openingnew perspectives in the field of remote rehabilitation.
  • Journal article
    Peters D, Sadek M, Ahmadpour N, 2023,

    Collaborative workshops at scale: a method for non-facilitated virtual collaborative design workshops

    , International Journal of Human-Computer Interaction, Pages: 1-18, ISSN: 1044-7318

    This article introduces a method for conducting a fully online collaborative design workshop requiring no facilitation which we refer to as a Self-guided Collaborative Online Workshop (SCOW). The article provides three main contributions. Firstly, we present a process for the conversion of a face-to-face facilitated design workshop into a SCOW using a method we call the “playboard” which draws on concepts from CSCL literature. Secondly, we evaluate the efficacy of SCOWs using an iterative evaluation with 75 participants, including measures for participant satisfaction, subjective and objective learning outcomes, quality of the online and self-guided experience, and comparison with face-to-face workshops. Results across all measures indicate that the self-guided workshop was as successful as the in-person facilitated original. Moreover, participants reported advantages of the more scalable format including improved access to those with non-visible disabilities and in the Global South. Finally, based on our findings, we present a set of recommendations for others interested in using SCOWs as an inclusive and scalable way to support collaborative experiences.
  • Journal article
    Chard I, Van Zalk N, Picinali L, 2023,

    Virtual reality exposure therapy for reducing social anxiety associated with stuttering: the role of outcome expectancy, therapeutic alliance, presence and social presence

    , Frontiers in Virtual Reality, Vol: 4, Pages: 1-15, ISSN: 2673-4192

    Introduction: Although several trials have demonstrated the effectiveness of Virtual Reality Exposure Therapy (VRET) for reducing social anxiety, there is little understanding about the factors that lead to symptom reduction across different treatment designs. Such factors may include outcome expectancy, therapeutic alliance, presence (perception of being in the virtual environment) and social presence (perception of interacting with others). We report on findings from a pilot trial of VRET targeting social anxiety in people who stutter, and examine the association of these four factors with treatment outcome.Methods: People who stutter reporting heightened social anxiety (n = 22) took part in the trial after being recruited via online adverts. Remotely delivered VRET was administered to participants in three sessions across three weeks. Each session targeted both performative and interactive anxiety. A virtual therapist helped participants to engage with treatment strategies, whilst also guiding them through exercises.Results: Findings showed that presence and social presence were both negatively related to changes in fear of negative evaluation between pre- and post-treatment. However, presence, outcome expectancy and therapeutic alliance were positively related to changes in social anxiety symptoms. Furthermore, outcome expectancy and therapeutic alliance were quadratically related to fear of negative evaluation change. Nevertheless, the effect of presence on social anxiety, and the effects of presence and therapeutic alliance on fear of negative evaluation must be interpreted with caution as these were not large enough to reach sufficient statistical power. Therapeutic alliance did not mediate the relationship between outcome expectancy and treatment outcome.Discussion: These findings suggest that the current VRET protocol affected social anxiety and fear of negative evaluation differently. We discuss how presence may underlie these mixed associations. We also s
  • Conference paper
    Reyes-Lecuona A, Cuevas-Rodríguez M, González-Toledo D, Molina-Tanco L, Poirier-Quinot D, Picinali Let al., 2023,

    Hearing loss and hearing aid simulations for accessible user experience

    This paper presents an open-source real-Time hearing loss and hearing aids simulator implemented within the 3D Tune-In Toolkit C++ library. These simulators provide a valuable tool for improving auditory accessibility, promoting inclusivity and foster new research. The hearing loss simulator accurately simulates various types and levels of hearing loss, while the hearing aid simulator replicates different hearing aid technologies, allowing for the simulation of real-world hearing aid experiences. Both simulators are implemented to work in real-Time, allowing for immediate feedback and adjustment during testing and development. As an open-source tool, the simulators can be customised and modified to meet specific needs, and the scientific community can collaborate and improve upon the algorithms. The technical details of the simulators and their implementation in the C++ library are presented, and the potential applications of the simulators are discussed, showing that they can be used as a valuable support software for UX designers to ensure the accessibility of their products to individuals with hearing impairment. Moreover, these simulators can be used to raise awareness about auditory accessibility issues. Overall, this paper also aims to provide some insight into the development and implementation of accessible technology for individuals with hearing impairments.
  • Journal article
    Ratha A, Pinson P, Le Cadre H, Virag A, Kazempour Jet al., 2023,

    Moving from linear to conic markets for electricity

    , European Journal of Operational Research, Vol: 309, Pages: 762-783, ISSN: 0377-2217

    We propose a new forward electricity market framework that admits heterogeneous market participants with second-order cone strategy sets, who accurately express the nonlinearities in their costs and constraints through conic bids, and a network operator facing conic operational constraints. In contrast to the prevalent linear-programming-based electricity markets, we highlight how the inclusion of second-order cone constraints improves uncertainty-, asset-, and network-awareness of the market, which is key to the successful transition towards an electricity system based on weather-dependent renewable energy sources. We analyze our general market-clearing proposal using conic duality theory to derive efficient spatially-differentiated prices for the multiple commodities, comprised of energy and flexibility services. Under the assumption of perfect competition, we prove the equivalence of the centrally-solved market-clearing optimization problem to a competitive spatial price equilibrium involving a set of rational and self-interested participants and a price setter. Finally, under common assumptions, we prove that moving towards conic markets does not incur the loss of desirable economic properties of markets, namely market efficiency, cost recovery, and revenue adequacy. Our numerical studies focus on the specific use case of uncertainty-aware market design and demonstrate that the proposed conic market brings advantages over existing alternatives within the linear programming market framework.
  • Journal article
    Cullen A, Zhao L, Vigneri L, Shorten Ret al., 2023,

    Improving quality of service for users of leaderless DAG-based distributed ledgers

    , Distributed Ledger Technologies: Research and Practice, Vol: 2, Pages: 1-18, ISSN: 2769-6472

    Usability of distributed ledgers is crucial to their mainstream adoption, especially for enterprise applications in which most users do not wish to operate full node infrastructure. Some attempts have been made to solve the problem of user-node interaction for blockchains in which leaders assemble users’ transactions into blocks, but in the case of leaderless DAG-based ledgers such as IOTA, many of these solutions cannot be applied due to the absence of a shared mempool and the ability of nodes to issue blocks in parallel. In this work, we propose a user-node interaction mechanism for ledgers of this kind that is designed to balance user traffic across nodes and ensure the risk of a user experiencing a poor quality of service is low. Our mechanism involves users selecting nodes to issue their transactions to the ledger based on quality of service indicators advertised by the nodes. Simulation results are presented to illustrate the efficacy of the proposed policies.
  • Journal article
    Wu B, Ai W, Kirkaldy N, Bonkile M, Jiang Y, Naylor-Marlow M, Patel Y, Liu X, Wang H, Martinez-Paneda E, Offer GJet al., 2023,

    (Invited) Multi-Scale Battery Modelling: Understanding Coupled Electrochemical and Mechanical Effects

    , ECS Meeting Abstracts, Vol: MA2023-01, Pages: 1634-1634

    <jats:p> Lithium-ion batteries are a key enabler for a low-carbon future, however their performance and lifetime are influenced by complex and coupled electrochemical, thermal and mechanical factors across different length and time scales. In this talk, we explore the key degradation modes which limit battery lifetime and how multi-scale models can help describe these effects towards improved cell designs and device control. At the particle level, we explore how phase field fatigue models of cathode particles can be used to understand crack growth, leading to loss of active material [1]. Here, non-linear crack growth is observed due to the fatigue of material properties and crack merger, leading to a transition from slow to rapid crack growth rate. Use of these models can identify critical C-rates and particle sizes which mitigate cracking.</jats:p> <jats:p>At the continuum scale, we then investigate how these stresses evolve during cycling, with stress heterogeneities arising initially at the electrode-separator interface, but later propagating to the electrode-current collector interface [2]. We then extend this study to composite anodes of graphite and silicon, where highly non-linear behaviour is observed [3]. Here, the graphite phase provides the majority of the reaction current density at high state-of-charge operation, with this then shifting to the silicon phase at low state-of-charge operation, with hysteresis effects observed due to the silicon. This behaviour is attributed mostly to the different open circuit potentials of the two different phases. Finally, we explore how these effects propagate to the battery pack scale and highlight the divergence of material level performance from their real-world implementation [4].</jats:p> <jats:p>References</jats:p> <jats:p>[1] A coupled phase field formulation for modelling fatigue cracking in lithium-ion battery electrode partic
  • Journal article
    Peters D, 2023,

    Wellbeing Supportive Design - Research-Based Guidelines for Supporting Psychological Wellbeing in User Experience

    , INTERNATIONAL JOURNAL OF HUMAN-COMPUTER INTERACTION, Vol: 39, Pages: 2965-2977, ISSN: 1044-7318
  • Journal article
    Jones CM, Austin K, Augustus SN, Nicholas KJ, Yu X, Baker C, Chan EYK, Loosemore M, Ghajari Met al., 2023,

    An instrumented mouthguard for real-time measurement of head kinematics under a large range of sport specific accelerations

    , Sensors, Vol: 23, Pages: 1-15, ISSN: 1424-8220

    BACKGROUND: Head impacts in sports can produce brain injuries. The accurate quantification of head kinematics through instrumented mouthguards (iMG) can help identify underlying brain motion during injurious impacts. The aim of the current study is to assess the validity of an iMG across a large range of linear and rotational accelerations to allow for on-field head impact monitoring. METHODS: Drop tests of an instrumented helmeted anthropometric testing device (ATD) were performed across a range of impact magnitudes and locations, with iMG measures collected concurrently. ATD and iMG kinematics were also fed forward to high-fidelity brain models to predict maximal principal strain. RESULTS: The impacts produced a wide range of head kinematics (16-171 g, 1330-10,164 rad/s2 and 11.3-41.5 rad/s) and durations (6-18 ms), representing impacts in rugby and boxing. Comparison of the peak values across ATD and iMG indicated high levels of agreement, with a total concordance correlation coefficient of 0.97 for peak impact kinematics and 0.97 for predicted brain strain. We also found good agreement between iMG and ATD measured time-series kinematic data, with the highest normalized root mean squared error for rotational velocity (5.47 ± 2.61%) and the lowest for rotational acceleration (1.24 ± 0.86%). Our results confirm that the iMG can reliably measure laboratory-based head kinematics under a large range of accelerations and is suitable for future on-field validity assessments.
  • Journal article
    Kench S, Squires I, Cooper S, 2023,

    TauFactor 2: A GPU accelerated python tool formicrostructural analysis

    , Journal of Open Source Software, Vol: 8, Pages: 5358-5358
  • Journal article
    Attar HR, Foster A, Li N, 2023,

    Development of a deep learning platform for sheet stamping geometry optimisation under manufacturing constraints

    , Engineering Applications of Artificial Intelligence, Vol: 123, Pages: 1-23, ISSN: 0952-1976

    Sheet stamping is a widely adopted manufacturing technique for producing complex structural components with high stiffness-to-weight ratios. However, designing such components is a non-trivial task that requires careful consideration of manufacturing constraints to avoid introducing defects in the final product. To address this challenge, this research introduces a novel deep-learning-based platform that optimises 3D component designs by considering manufacturing capabilities. This platform was realised by developing a methodology to combine two neural networks that handle non-parametric geometry representations, namely a geometry generator based on Signed Distance Fields (SDFs) and an image-based manufacturability surrogate model. This combination enables the optimisation of complex geometries that can be represented using various parameterisation schemes. The optimisation approach implemented in the platform utilises gradient-based techniques to update the inputs to the geometry generator based on manufacturability information from the surrogate model. The platform is demonstrated using two geometry classes, Corners and Bulkheads, each having three geometry subclasses, with four diverse case studies conducted to optimise these geometries under post-stamped thinning constraints. The case studies demonstrate how the platform enables free morphing of complex geometries, while also guiding manufacturability-driven geometric changes in a direction that leads to significant improvements in component quality. For instance, one of the cases shows that optimising the complex component geometry can reduce the maximum thinning from 45% to satisfy the thinning constraint of 10%. By utilising the proposed platform, designers can identify optimal component geometries that ensure manufacturing feasibility for sheet stamping, reducing design development time and design costs.
  • Journal article
    Harrison J, Lucas A, Cunningham J, McPherson AP, Schroeder Fet al., 2023,

    Exploring the opportunities of haptic technology in the practice of visually impaired and blind sound creatives

    , Arts, Vol: 12, ISSN: 2076-0752

    Visually impaired and blind (VIB) people as a community face several access barriers when using technology. For users of specialist technology, such as digital audio workstations (DAWs), these access barriers become increasingly complex—often stemming from a vision-centric approach to user interface design. Haptic technologies may present opportunities to leverage the sense of touch to address these access barriers. In this article, we describe a participant study involving interviews with twenty VIB sound creatives who work with DAWs. Through a combination of semi-structured interviews and a thematic analysis of the interview data, we identify key issues relating to haptic audio and accessibility from the perspective of VIB sound creatives. We introduce the technical and practical barriers that VIB sound creatives encounter, which haptic technology may be capable of addressing. We also discuss the social and cultural aspects contributing to VIB people’s uptake of new technology and access to the music technology industry.

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