Open Research Exeter - University of Exeter
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Identifying Opportunities for Uncrewed Vessel Technology in Offshore Wind Projects Using Automatic Identification System (AIS) Data
No full textAutomatic Identification System (AIS) data holds significant potential for capturing and analysing activities at sea. For offshore wind developers and operators seeking lower emissions using uncrewed surface vessels (USVs) and other alternatives to conventionally crewed vessels, analysis of AIS enables understanding of how such craft can be incorporated into different operations. This research presents a methodology, using archived AIS data to trace the movements of vessels and identify relevant activities. Our findings demonstrate how archived AIS data combined with both public sources of contextual information and expert knowledge regarding the activities, can enable the characterization of previous site investigation surveys and the inspection of subsea structures, and so identify specific applications of USVs in these scenarios throughout the development and operation of offshore wind projects.</p
Balancing Fidelity and Computational Efficiency in Mooring System Simulations for Floating Offshore Wind Turbines
No full textFloating Offshore Wind Turbines (FOWTs) are nearing commercial deployment, expanding offshore wind development opportunities to deeper waters beyond the reach of bottom-fixed turbines. Reducing the capital and operational costs of FOWTs is essential, with mooring systems identified as a key area for cost savings. High-fidelity, coupled, time-domain simulations ensure a mooring design’s suitability for a particular site, considering the full range of environmental conditions, but this process can be computationally demanding. During early design and optimization, lower-fidelity simulations enable exploration of a wider envelope of configurations at the cost of reduced model accuracy.This paper quantifies the trade-off between computational efficiency and model-to-model accuracy when reducing simulation fidelity. Using the IEC 15 MW turbine atop the UMaine VolturnUS-S platform with semi-taut and catenary mooring configurations, the study examines methods of reducing model fidelity with time and frequency domain approaches. Findings show strategic fidelity reduction, such as replacing the turbine with a lumped mass and applying a constant force, reduces computation by up to 96 %, while maintaining errors within 10 % for key performance parameters and enabling relative fatigue assessment. However, omitting critical elements like the control system may increase error without saving computational time. This work informs efficient mooring optimization strategies for FOWTs.</p
Mass invariant in a compressible turbulent medium
No full textPredicting the measurable statistical properties of density fluctuations in a supersonic compressible turbulent
flow is a major challenge in physics. In 1951, Chandrasekhar derived an invariant under the assumption of
the statistical homogeneity and isotropy of the turbulent density field and stationarity of the background density.
Recently, Jaupart and Chabrier [Astrophys. J. Lett. 922, L36 (2021)] extended this invariant to nonisotropic flows
in a time-evolving background and showed that it has the dimension of a mass. This invariant Minv is defined
by Minv = E(ρ)Var( ρ
E(ρ) )(lρ
c )3, where ρ is the density field and lρ
c is the correlation length. In this article, we
perform numerical simulations of homogeneous and isotropic compressible turbulence to test the validity of this
invariant in a medium subject to isotropic decaying turbulence. We study several input configurations, namely
different Mach numbers, injection lengths of turbulence, and equations of state. We confirm that Minv remains
constant during the decaying phase of turbulence. Furthermore, we develop a theoretical model of the density
field statistics which predicts without any free parameter the evolution of the correlation length with the variance
of the log-density field beyond the assumption of the Gaussian field for the log density. Noting that Minv is
independent of the Mach number, we show that this invariant can be used to relate the non-Gaussian evolution
of the log-density probability distribution function to its variance with no free parameters
Evaluating GEDI for quantifying forest structure across a gradient of degradation in Amazonian rainforests
No full textForest structure is key to understanding the resilience of tropical forests (their ability to recover from disturbance) and predicting how these ecosystems will respond to future environmental and climatic fluctuations. Current resilience studies in the Amazon rely on passive and active remote sensing forest cover metrics that offer limited insight into nuanced forest canopy structural changes associated with degradation. The Global Ecosystem Dynamics Investigation (GEDI) spaceborne lidar provides detailed information on canopy structure, a key factor in forest recovery, resilience, and ability to provide ecosystem services. We evaluate GEDI spaceborne lidar’s capability to characterise forest structure along a gradient of degradation (e.g. primary unburned (PU), secondary recovering, fire frequency), and investigate the potential of quantifying forest structure to advance understanding of forest responses to disturbance across the Amazon. We assess the correspondence of GEDI structural metrics such as relative height (RH) and canopy cover to airborne lidar metrics across the Brazilian Amazon using Lin’s concordance correlation coefficient (CCC). We evaluate GEDI forest structure variation along a gradient of forest degradation. We explore the potential of principal component (PC) analysis applied to GEDI data to derive a continuous descriptor of forest structural state that characterises the forest degradation continuum, and use a multinomial logistic regression model (MNLR) to further evaluate this descriptor. The strongest positive correspondence for all sampled GEDI and airborne lidar footprints occurs at RH96 (CCC; 0.57) of the canopy height profile, with strongest agreement in primary forest burned at least three times (CCC; 0.91). Whilst canopy cover showed significant recovery 15-25 years after disturbance, forest canopy height and aboveground biomass density had not fully recovered to pre-disturbance levels within 38 years. The PCA identified the importance of RH75, RH96, foliage height diversity index and canopy directional gap probability, with PC1 and PC2 explaining 80% and 15% of variance, respectively. The MNLR suggests that the ratio of these PCs effectively characterises the forest degradation gradient. We demonstrate the ability of GEDI 2A/B structural metrics to differentiate forest structure along a gradient of PU to secondary severely degraded forest in the Amazon rainforest, despite some overlap in structural characterisations between similar degradation classes. Our new method for deriving a forest structural state metric supports future research on forest monitoring, conservation, and the study of Amazon-wide ecosystem resilience
Acceptability and feasibility of a novel postural management night-time intervention to improve respiratory health of children and young people with complex neurodisability (Breathe-Easy): proof of concept study
No full textObjectives:
Children and young people with complex neurodisability (CYPCN) are at high risk of respiratory illness, frequent hospital admissions and premature death. This study aimed to test the acceptability and feasibility of Breathe-Easy, a novel night-time postural intervention to improve respiratory health in CYPCN.
Design:
Mixed methods design incorporating a pre-post interventional study and qualitative study.
Setting:
Intervention conducted at home by parents/carers.
Participants:
CYPCN aged 2-18 years, dependent on others to move, swallowing difficulties, gastrostomy/jejunostomy, and under care of a respiratory paediatrician.
Intervention:
Breathe-Easy protocol included CYPCN lying on a flat bed, three-quarters prone or side-lying using existing night-time positioning equipment. A bile-bag was used to minimise reflux. CYPCN trialled intervention for 6 months.
Main outcome measures:
Measures of respiratory health and sleep were collected at baseline, three and six months. Semi-structured interviews were conducted with parents, CYPCN, and healthcare professionals post intervention. Data analysis comprised descriptive statistics and thematic analysis. improved during the intervention.
Results:
Eleven CYPCN were recruited; eight completed the trial. We interviewed 5 CYPCN, 9 parents, 8 healthcare professionals, 6 carers and one teaching assistant. Positive views were expressed regarding sleep quality, breathing, secretion management and reduced hospitalisation. Overall improvement in respiratory health and sleep measures. All eight participants planned to continue with Breathe-Easy.
Conclusion:
Breathe-Easy appears acceptable and feasible. Further research will need to evaluate feasibility of implementation by other teams and families, and any impact on progressive musculoskeletal deformity, including addressing methodological challenges gathering key outcomes and adverse events
Disorder
No full textThis paper begins with some brief intellectual autobiography, recalling my first engagement with philosophy of biology. The substantive part of the paper then focuses on the plurality of possible classifications central to the theses of scientific disunity and metaphysical disorder developed in my early career. After discussing this in terms of biological classification, and introducing the reasons for thinking of classifications as typically value-laden, I discuss two sets of human classifications bearing on normatively vital questions, those around sex and gender and those involved in the distinctions between human races
Wet storage of floating wind turbines
No full textMany governments have a number of ambitious targets to increase electricity generation by
renewable energy in order to achieve Net Zero by 2050. To meet these targets, the requirement for new wind farms in deeper waters has led to increasing interest in the opportunities of floating offshore wind turbines (FOWT). Existing Floating Offshore Wind projects are small-scale demonstrator projects. Future commercial-scale projects with a generation capacity of 1GW could result in novel and more significant impacts on construction schedules.
Management of wet storage sites – Floating Offshore Wind introduces new potential impact areas in coastal waters where turbines might be temporarily moored during construction or maintenance.
Offshore wind farms have not directly impacted inshore vessel traffic, ship anchorages, port approaches, and coastal aerodromes. The use of wet storage imposes new
potential impacts on the maritime industry.
A reoccurring theme for construction and installation is the concern over wet storage requirements for FOWFs. Environmental Impact Assessments (EIAs) for OWF have typically comprised of three components: the array area, the offshore export cable route, and the onshore export cable route to the substation. However, wet storage (which is principally a concept that is useful for construction logistics), involves the temporary storage of either partially or fully constructed floating offshore wind turbines in port or coastal waters.
It is expected that many substructures may be wet stored simultaneously during the construction of a commercial-scale project. Whilst it is feasible that major maintenance campaigns or even construction could occur at wet storage sites, tow to shore, the size of Floating Offshore Wind Turbines, depth of water and current capabilities of large crane vessels likely make this impractical. Given that wet storage sites are likely to be essential to construction strategies for commercial-scale Floating Wind Farms, their potential impacts could be significant. However, this assessment of wet storage is constrained by the uncertainties as to where such sites would be located and therefore prevents a full assessment
Rewinding the tape: experimental evolution of resistance to glyphosate
No full textModern agriculture relies on chemical weed control to secure crop yields, but extensive and prolonged herbicide use has imposed strong selective pressures, driving the evolution of resistance in weeds and contaminating non-target ecosystems. Understanding the evolutionary dynamics and outcomes of herbicide selection is critical for addressing these challenges. Microbial model organisms, such as the green alga Chlamydomonas reinhardtii, provide an ideal system to study resistance evolution in a controlled laboratory setting, and represents an important group of non-target organisms exposed to herbicide pollution.
This thesis examines the effects of glyphosate selection on adaptation in C. reinhardtii. Specifically, the study focused on the evolutionary dynamics, fitness, and genomic changes associated with exposure of C. reinhardtii to this herbicide, linking resistance phenotypes to genomic changes under contrasting selection regimes. While most research has focused on sudden exposure to high herbicide doses, gradual dose increases can occur due to the accumulation of herbicides in the environment, with potentially distinct evolutionary impacts. Using experimental evolution and whole genome sequencing, adaptive responses were investigated under two ecological scenarios. The first experiment involved a simple scenario with a single rapid glyphosate dose increase, while the second tested a complex scenario with variable changes in dose rates (rapid, intermediate, and slow rates of change).
The findings from these experiments revealed that rapid dose increases augmented variability and delayed resistance evolution, whereas gradual changes imposed fitness costs. Genome-wide variant detection indicated that glyphosate resistance was not associated with mutations or copy number variation in the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Instead, evidence suggests that glyphosate resistance in C. reinhardtii is driven by non-target-site mechanisms, regardless of selection history. Furthermore, limited overlap in resistance-associated loci between treatments and replicates suggests a complex, and potentially independent, evolutionary response to glyphosate selection. These insights contribute to our understanding of the evolutionary and genomic mechanisms driving herbicide resistance
Nonequilibrium models of population dynamics can reveal the causes of the demographic transition
No full textNonequilibrium models of population dynamics can reveal the causes of the demographic transition
Understanding the motivations of small-scale miners in Yukon, Canada through a human-nature connection (HNC) framework and meaningful rural work
No full textHuman–nature connections (HNCs) experienced by a community of miners are explored as drivers of small-scale mining in Yukon, Canada. Through 20 placer mine visits and 32 semi-structured interviews with miners, government, and suppliers, the study finds that a connection to nature—not profit—is the primary motivation. Using a HNC framework, the data reveal that miners perceive their livelihoods as meaningful rural work tied to their engagement with the land and natural environment. These connections go beyond material needs, encompassing experiential, cognitive, emotional, and philosophical realms. Yukon miners' ability to make localized decisions and participate in the full mine life cycle highlights the importance of autonomy and proximity to nature. The concept of mining as an ecosystem service emerges when Earth materials are included within the definition of nature. This study challenges dualistic paradigms that separate humans from nature and Earth material needs, and contributes to broader efforts to embed strong sustainability in the mining sector—an approach that recognizes nature as the non-substitutable foundation of all other forms of capital. It also identifies the fragility of HNCs in contexts where excessive stress on ecosystems, remote decision-making, or livelihood insecurity undermines sustainability. Yukon provides a case study for exploring alternative mining models, such as slow mining, which emphasizes responsible practices and local empowerment. These insights contribute to human–nature debates and point toward more sustainable, place-based mining frameworks grounded in strong sustainability principles