Performance investigation of an oscillating-body WEC with the tristable energy capture mechanism

This paper conducts an investigation into the energy harvesting performance of a tristable wave energy converter (WEC) utilizing a dual snap-through mechanism. Existing studies have indicated that the bistable characteristics inherent in such mechanisms can substantially improve the power output of oscillating-body WECs. The dual snap-through mechanism comprises four symmetrically configured inclined springs, with its energy harvesting behavior being highly dependent on the geometric arrangement and stiffness of the springs. A distinctive feature of the tristable system is the emergence of three potential wells. Following the development of a mathematical model for the nonlinear WEC, this study first examines the mechanism through which multiple potential wells contribute to enhanced energy conversion. Subsequently, a comprehensive parameter analysis is conducted to evaluate the influence of variations in the parameters of the dual snap-through mechanism and wave amplitudes on the energy conversion. The results demonstrate that appropriate stiffness and projected lengths of the springs can markedly improve the power output of the WEC. Furthermore, by adjusting the parameters of tristable mechanism, the WEC can achieve superior energy generation even at high wave frequencies or under low-amplitude excitation. Finally, the current study can offer some valuable insights for the design of other multistable WECs

Tour guides as climate change agents : conceptualizing meaningful work through agency theory in precarious employment

This paper addresses the mediating role of tour guides in educating tourists in climate-sensitive regions. Such a role is crucial for fostering awareness of climate change and encouraging environmentally responsible behaviour. The study focuses on the Mekong Delta, a region highly vulnerable to climate impacts, where tourism is both a livelihood source and a potential driver of climate action. Employing Agency Theory, we examine how tour guides in this setting find meaning in their work as climate change advocates, drawing on in-depth interviews with 43 casual-work tour guides. Findings reveal that tour guides in the Mekong Delta derive significant personal and professional meaning from promoting climate awareness among tourists

A steady-state model for tilting pad journal bearings incorporating an analytical extension of the Sommerfeld solution

An analytical model for a tilting pad journal bearing has been developed by adapting a correction factor method previously used for standard journal bearings. The approach derives the Sommerfeld solution for an infinitely long tilting pad bearing and uses it to adjust the centerline pressure of an infinitely short bearing. This semi-analytical solution addresses a gap in the literature on finite-length tilting pad bearings. Analytical models offer valuable insights into variable interactions and enable faster computation, useful in systems with fluctuating loads, like energy transmission systems. Validation across varying journal speeds and load directions showed a maximum error of 23.5% on the most loaded pad, demonstrating the model’s usefulness in early-stage design, mapping operational envelopes, and assessing bearing suitability

Hydrogen–diesel dual-fuel combustion in marine medium-speed engines : knocking suppression by direct water injection at high hydrogen substitution ratios

Hydrogen is among the most promising alternative fuels for achieving zero-carbon emissions in the maritime sector. However, its application in marine engines faces the bottleneck of substitution ratio limitation. The primary reason is the risk of knocking resulting from hydrogen's rapid heat release and high flame speed. The aim of this study is to explore in-cylinder direct water injection as a knocking-suppression strategy to enable higher hydrogen fractions in the engine. Two knocking-free operating modes are investigated: low hydrogen substitution ratios (0–40 %) without water injection and high hydrogen substitution ratios (90 and 95 %) with water injection. The results show that without water injection, the maximum hydrogen substitution ratio that can maintain stable combustion is 30 %, resulting in a 2.96 % improvement in indicated thermal efficiency and a 3.11 g/kWh rise in NOx emission. With direct water injection, knocking-free combustion can be achieved at high hydrogen substitution (90 and 95 %) under specific injection timing. At the suggested control point of 90 and 95 % HSR (1.5 water-to-fuel ratio, and −100 °CA water injection timing), a 1.43 % and 1.39 % improvement in indicated thermal efficiency and a 6.01 g/kWh and 6.45 g/kWh reduction in NOx emissions can be achieved compared to pure diesel mode. These findings indicate that in-cylinder direct water injection effectively increases hydrogen substitution ratios while enabling high thermal efficiency and low emissions, making it a promising approach for hydrogen–diesel dual-fuel marine engines

Single transmission phase- and frequency-modulated coded excitation for enhanced inspection of thick complex industrial components using a scalable, flexible, lead-free, ultrasonic array

To address the growing challenge of applying ultrasonic non-destructive evaluation to complex industrial components, flexible ultrasonic arrays have emerged as a conformable solution to inspect such geometries, thereby removing the need for custom-designed wedges to conform to surfaces. Flexible lead-based arrays have been used in prior research. They offer high piezoelectric coefficient, however, they pose human health and environmental risks, and fail to comply with global initiatives including the Restriction of Hazardous Substances (RoHS) regulation enacted by the European Union. Although numerous studies on the piezoelectric properties of lead-free materials have been conducted, the uptake of technology and implementation in practice has been slow. In this work, a scalable, RoHS-compliant, flexible ultrasonic array was employed to improve operability in thick convex and concave components. However, the lead-free array exhibits lower piezoelectric coefficient compared to its lead-based counterparts, resulting in reduced signal quality. To tackle this shortcoming, single transmission phase-modulated Barker and frequency-modulated chirp excitation schemes, in conjunction with pulse compression, were employed to improve the signal quality. Subsequently, their impact was studied in terms of imaging quality, through Full Matrix Capture (FMC) acquisition methodology and Total Focusing Method (TFM) imaging, and Signal-to-Noise Ratio (SNR) measurements. A novel SNR method was presented. Existing SNR approaches evaluate image quality by calculating it within a designated area surrounding the target, where the noise level is quantified as the root mean square of the image noise, omitting any indication of the target. In addition to the noise level, artifacts from matched filters and sidelobes require quantitative evaluation. The new SNR technique was proposed to automate the selection of regions when characterising the SNR. The SNR was calculated across regions of varying size, with the region size where the SNR values converged being selected. This technique was utilised in a comparative analysis including a single-cycle pulse excitation, modulated Barker and chirp excitation schemes with equivalent energy levels in simulation and experimentally. The simulated and experimental results showed good agreement, with some discrepancies attributed to imperfections in the experimental conditions. SNR improvement exceeding 2.6 dB was observed experimentally, with the coded excitation techniques showing higher SNR and better image quality without sacrificing acquisition speed. Moreover, sidelobe artifacts were evident in all TFM images, while the coded excitation images further exhibited matched filter processing artifacts. The flexibility of the array was assessed in the subsequent two experiments to determine its effectiveness in improving operability in complex-geometry samples. The convex and concave samples pre-aligned the array to promote a converging and diverging ultrasonic beam, respectively. In all cases, the array demonstrated excellent conformity with the components, and the coded excitation schemes consistently achieved better imaging quality relative to the pulse excitation case

Gender, violence and nuclear weapons

In this chapter, we seek to bridge previously separated scholarship on gender violence and nuclear violence. In the first part, we show how these separate academic fields may have distinct conceptual trajectories but also speak to each other in productive ways, most obviously in feminist-informed work on nuclear politics. In the second part, we show how this feminist-informed work illuminates both the material and discursive dimensions of nuclear violence. We reverse our focus in the third and final part to argue that the literature on nuclear violence can push feminist thinking on gender and violence in more expansive and inclusive directions. In making these arguments, we hope to contribute to an ongoing discussion on the intertwining of gender violence and nuclear violence, and how we might end both

A hybrid floating wind-wave energy platform for minimum power baseload

We develop a novel hybrid wind-wave energy platform for applications that require a minimum power baseload for continuous operation. The hybrid platform consists of three very large pontoons connected with mechanical hinges. The downstream pontoon carries a 5 MW wind turbine on deck. Wave energy is extracted trough hinge motion. By computing numerically a power matrix for wave energy conversion, and assuming mean power production for the wind turbine, we evaluate the performance of the hybrid platform. Rather than assessing performance in terms of power variability, performance is gauged by determining periods of time when the hybrid platform meets a minimum power threshold, in periods of time of absent wind power. The platform is assessed in three locations with different wind-wave correlation characteristics: One off the coast of Spain, one on the West and one on the East coast of Scotland. It is found that the platform has better performance in locations with high wave power density and low to intermediate wind-wave correlation indices. The hybrid concept, besides being modular and scalable, can meet the requirements of recently considered steady state applications to be deployed offshore. For example, hydrogen electrolysers, which require a minimum power supply for lasting operation

Supporting their school communities during and in the aftermath of lockdown : changing perceptions of former Into Headship students of their role and its perceived impact on the school community

This chapter focusses on a study which examined how former students on a national headship preparation programme in Scotland (Into Headship [IH]) supported their school communities in the recovery period of the pandemic beyond the initial lockdown in the spring of 2020 in their roles as senior leaders. It illuminates the experiences of two Depute Headteachers from the primary and special education sectors respectively. This constitutes the 2nd phase of a longitudinal, qualitative study, conducted in Dec 2022/Jan 2023 via individual interviews and focus group discussions with eight respondents to an initial survey drawn from the secondary, primary and special education sectors. The chapter explores not only the actions taken to support the school community and their perceived efficacy, but how the multiple, dynamic transitions experienced by the former students affected perceptions of their role and sense of identity. Further, this chapter illustrates how their experiences had a ripple effect across the transitions experienced by other members of the school community, including staff, parents/carers and pupils, linking this to Jindal-Snape’s (2023) Multiple and Multi-dimensional Transitions (MMT) Theory, ecological theory, and Gale and Parker’s (2014) concept of transition as becoming

High-performance curved sections in 3D printed continuous carbon fibre reinforced thermoplastic composites using aligned fibre deposition

This paper presents high-performance curved sections in 3D printed continuous carbon fibre reinforced thermoplastic composites using an aligned fibre deposition (AFD) method on a 6-axis robotic arm. 3D printed curved composite beams using both AFD and conventional methods are mechanically tested under four-point bending and scanned by X-ray computed microtomography (μCT) to characterise the fibre distribution and develop image-based finite element models. Compared to conventional printing method using a commercial nozzle, the proposed AFD method significantly improves the fibre alignment and reduces void content in the printed composites, and the curved beam strength is calculated as 204.2 N and 224.5 N for the cases of 7 mm and 15 mm radius of curvature, achieving an improvement of 34.0 % and 45.3 %, respectively. The modelling produces excellently matched stiffness with the experimental measurement, providing useful insights into the stress and strain distributions. The combination of experimental data and modelling results shows that the alignment of fibres in the curved composite beams plays a key role in improving mechanical performance and determining the final failure mode

Advanced optimisation software framework for floating offshore wind farm logistics and operations

Offshore wind farms are being built farther from shore to maximise energy production, but this creates significant logistical challenges for maintaining these remote turbines. Service Operation Vessels (SOVs) and Crew Transfer Vessels (CTVs) play a vital role in keeping turbines operational. However, their routes need to be carefully planned to reduce travel distances and fuel consumption while meeting tight maintenance schedules. This study introduces a Python-based optimisation framework designed to streamline both day-to-day and campaign-style maintenance operations. By integrating geospatial analysis, clustering algorithms, and multi-day scheduling, the framework generates efficient vessel routes considering different turbine locations, weather windows, technician capacity, and vessel availability. When full daily servicing is unfeasible, the framework prioritises tasks and creates multi-day schedules to ensure efficient use of resources. Clustering techniques further streamline the process by grouping nearby turbines for maintenance. A real-world case study demonstrated a 36 % reduction in fuel consumption compared to conventional methods, underscoring the framework's potential to lower operational costs and enhance sustainability. In addition to this efficiency gains, the solution mitigates risks by ensuring timely maintenance, thereby supporting the offshore wind sector's capacity to meet escalating energy demands reliably