Tunnelling-induced wall damage: An appraisal of elastoplastic constitutive models for masonry

This paper investigates the role of masonry elastoplastic constitutive models on tunnelling-induced damage in buildings. A two-stage analysis method (TSAM) is adopted, incorporating input greenfield displacements, 3D masonry walls, and an elastic model for the soil. The paper focuses on four masonry constitutive models that can be readily adopted for routine analysis in industry. Comparison of in-plane yield surfaces with experimental data indicates that, among the considered masonry models, the Concrete Damaged Plasticity model under biaxial calibration gives the best overall performance. The TSAM is then used to study selected tunnel-masonry wall scenarios, confirming a significant effect of the constitutive model and its parameters on masonry wall response to tunnelling, particularly after volume losses where moderate damage is triggered. Also, as masonry stress paths are shown to concentrate in the tensile–compressive areas, with damage prediction being sensitive to the yield surface within this quadrant, numerical damage predictions must rely on the accurate calibration of the constitutive model in the tensile–compressive quadrants. This appraisal indicates that, in the context of routine structure modelling for tunnelling assessments, the selection of elastoplastic masonry models and their biaxial calibration have a non-negligible impact on the damage category estimate

Optimizing photovoltaic thermal systems with wavy collector Tube: A response Surface-Based design study with desirability analysis

A comprehensive simulation model and predictive analysis are employed to investigate the performance of a photovoltaic thermal (PVT) system with a wavy collector tube. Response surface methodology and desirability analysis are utilized to develop a robust model that considers five critical design variables: collector wavelength, amplitude, diameter, panel width, and fluid inlet velocity. The complex interactions between these variables and their impact on the system’s energy and exergy outputs are thoroughly examined. Single and multi-objective optimization techniques are strategically applied to maximize the PVT system’s performance under various operating conditions. The results reveal that the wavy tube configuration achieves superior electrical and thermal energy efficiency compared to the conventional straight-tube design. The system’s performance is significantly enhanced by optimizing the collector amplitude, inlet velocity, diameter, wavelength, and panel width. The optimized wavy-tube PVT system demonstrates remarkable overall energy and exergy efficiencies of 85% and 14.67%, respectively, outperforming the baseline straight-tube system’s efficiencies of 72.41% and 12.72%. This research provides valuable insights into the optimal design of PVT systems and contributes to the advancement of PVT technology. The findings highlight the potential for widespread implementation of highly efficient and sustainable PVT systems in the renewable energy sector

Additive manufacturing of functionalised atomic vapour cells for next-generation quantum technologies

Atomic vapour cells are an indispensable tool for quantum technologies (QT), but potential improvements are limited by the capacities of conventional manufacturing techniques. Using an additive manufacturing (AM) technique—vat polymerisation by digital light processing—we demonstrate, for the first time, a 3D-printed glass vapour cell. The exploitation of AM capacities allows intricate internal architectures, overprinting of 2D optoelectronical materials to create integrated sensors and surface functionalisation, while also showing the ability to tailor the optical properties of the AM glass by in-situ growth of gold nanoparticles. The produced cells achieve ultra-high vacuum of 2 × 10−9 mbar and enable Doppler-free spectroscopy; we demonstrate laser frequency stabilisation as a QT application. These results highlight the transformative role that AM can play for QT in enabling compact, optimised and integrated multi-material components and devices

Investigation of support structure configurations for selective laser melting of In718

The Selective Laser Melting (SLM), as a widely used metallic Additive manufacturing (AM) process, relies heavily on support structures. This study investigated the impact of different support structure configurations on the quality of In718 samples fabricated through SLM. On the basis of a comprehensive review of existing support structures configurations from the literature, three typical configurations: block, cone, and lattice, were designed to support cantilever parts for performance comparison. A coupled thermo-structural finite element simulation using ANSYS was performed to evaluate the temperature, deformation, and thermal stress evolution during the printing process of the three supported cantilever structures. The residual stress and deformation of the printed In718 cantilevers with different support structures were measured for validation. The results showed that block support exhibits the best strength and heat dissipation capability, making it the most effective support configuration for the SLM of In718 material. This research provides a fundamental procedure for evaluating the supporting performances among various support structures for the SLM process

Online Harmonic Reduction for Aircraft Electrical Power Distribution System With Global Phase-Shifted Carrier PWM

The penetration rate of power electronics converters (PEC) within onboard electrical power distribution systems (EPDS) has been rising for years due to the trend of moving towards more electric aircraft (MEA) and all electric aircraft (AEA). Digital control and pulse width modulation (PWM) of these devices give rise to the electrical harmonics within the EPDS. Phase-shifted carrier PWM (PSC-PWM) has been a well-established concept for cascaded/paralleled PECs to eliminate certain harmonic components. However, when multiple PECs work cooperatively with different power ratings in the EPDS, an exhaustive system-level analytical model accurate to switching behavior is difficult to acquire and solve in real-time. In this work, a Simulated Annealing-based global optimization method is proposed for further enhancing the waveform quality at the EPDS transmission bus by tuning the PSC offset angle of the PECs directly according to the total harmonic distortion (THD) value measured online. Simulation and experimental results are given with a three-port system to verify the proposed scheme

Laplace-based strategies for Bayesian optimal experimental design with nuisance uncertainty

Finding the optimal design of experiments in the Bayesian setting typically requires estimation and optimization of the expected information gain functional. This functional consists of one outer and one inner integral, separated by the logarithm function applied to the inner integral. When the mathematical model of the experiment contains uncertainty about the parameters of interest and nuisance uncertainty, (i.e., uncertainty about parameters that affect the model but are not themselves of interest to the experimenter), two inner integrals must be estimated. Thus, the already considerable computational effort required to determine good approximations of the expected information gain is increased further. The Laplace approximation has been applied successfully in the context of experimental design in various ways, and we propose two novel estimators featuring the Laplace approximation to alleviate the computational burden of both inner integrals considerably. The first estimator applies Laplace’s method followed by a Laplace approximation, introducing a bias. The second estimator uses two Laplace approximations as importance sampling measures for Monte Carlo approximations of the inner integrals. Both estimators use Monte Carlo approximation for the remaining outer integral estimation. We provide four numerical examples demonstrating the applicability and effectiveness of our proposed estimators

Event-based chessboard scanning profilometry

Event-based structured light profilometry shows great promise for three-dimensional (3D) shape measurement. However, existing methods face limitations in sampling efficiency. To address these limitations, an event-based chessboard scanning method for 3D shape measurement is proposed. It achieves orthogonal multi-edge scanning with a chessboard pattern sequence, leveraging the advantage of edge scanning over line scanning to reduce redundant sampling. Additionally, it facilitates the simultaneous indexing of multiple event lines through event-phase mapping and phase unwrapping. Furthermore, event drift is investigated and an energy flow sub-pixel compensation algorithm is proposed to mitigate its effects. Experimental results validate the satisfactory accuracy of the proposed method and demonstrate its efficacy and robustness in measuring objects with complex shapes in both static and dynamic scenarios

Perception and acquaintance of stroke specialists on non-inferiority trials: An international survey

Introduction: The adoption of non-inferiority trial designs for assessing new interventions in stroke treatment is on the rise. We designed a survey to assess stroke specialists' understanding and familiarity with non-inferiority trials and margins. Methods: A brief web-based questionnaire was sent to the members of the World Stroke Organization (WSO). The median acceptable non-inferiority margins in different research settings provided by responders were summarized and reported according to the acquaintance of responders with non-inferiority trials. Results: A total of 120 WSO members from 42 countries responded to the survey. Thirty-two percent (32 %) of respondents self-identified as being very familiar with non-inferiority trials, while 6 % identified as extremely familiar. When asked about the impact of non-inferiority trials on improving stroke patient care, 42 % rated it as high and 45 % as moderate. 83 % of responders reported that the findings of non-inferiority trials affect their clinical practice. Ease of administration, relative effect of the standard treatment, clinical implications of inappropriately introducing the new treatment, availability, price, ease of storage and shipping were all considered as factors that should influence the size of the non-inferiority margin. The magnitude and variability of acceptable non-inferiority margins were seen to decrease as the acquaintance of responders with non-inferiority trials increased. Conclusion: Although responders acknowledge the importance of non-inferiority trials, most have limited acquaintance with this research design. Educational activities are needed to enhance literacy in non-inferiority trials and the interpretation of non-inferiority margins

The Role of AI Feedback in University Students’ Learning Experiences: An Exploration Grounded in Activity Theory

This study employs Engeström’s second-generation activity theory (AT) to examine the transformative potential of Generative AI (GenAI) in providing formative feedback in higher education. Specifically, this research focuses on the experiences of fifty students with generic and calibrated GenAI feedback in a graduate program in the US. Through the analysis of participants’ multimodal views and textual reflections after their experiences with these two types of AI reviews, we uncover the role that the AI reviewer played in the peer and AI review activity system of which students were part. The examination of the semiotic elements embedded in the participants’ artifacts points to clear opinion differences in connection with the effectiveness and role of generic and calibrated AI feedback in the review activity system. The results show that while the generic AI reviewer was deemed an imperfect, limited tool, its calibrated counterpart was welcomed by students for its effectiveness and was even regarded by some participants as a new member of the community of practice within the activity system. Based on the findings resulting from this investigation, we suggest effective strategies for AI-human collaboration in higher education, aiming to enhance teaching and learning practices through advanced AI applications

Contesting monuments: Heritage and historical geographies of inequality, an introduction

This paper introduces a virtual special issue that explores how monuments have been contested in the past and how they continue to be so in the present. A survey of papers published in this journal from the 1990s to the early-2000s demonstrates an ongoing and rich interest in the interconnections between nationalism, landscape and ritual, with some emphasis on resistance but little sense of the contemporary lives of these historic monuments. Broader geographical scholarship in the mid-2000s evidenced the memory boom that was taking place across the discipline, beyond historical geography. A second survey of papers in this journal, published from 2012 to 2021, evidences a richer engagement with post-colonial, post-Soviet and post-slavery periods and perspectives, and with a broader range of sites beyond Europe and North America. More recent scholarship has focused on participatory geography, calls for statues to fall, and for more experimental, non-representational methods. This introduction concludes by summarising the papers in this special issue and reflecting on the relationships between monuments and contestation that they create, namely: monuments to contestation; the historic contestation of monuments; and the ongoing contestation of monuments as heritage spaces (attacks and felling, retaining and explaining, re-using, creating counter-monuments, artistically re-symbolising and re-imagining monuments, and contestatory scholarship)