Open Research Exeter - University of Exeter
Not a member yet
41213 research outputs found
Sort by
Stiffness-proportional foundation damping to linearise soil-monopile interaction models for wind turbines (dataset)
No full textNo description availabl
Exploring Sentinel-1 Radar Polarisation and Landsat Series Data to Detect Forest Disturbance from Dust Events: A Case Study of the Paphos Forest in Cyprus
No full textMonitoring forest health has become essential due to increasing pressures caused by climate change and dust events, particularly in semi-arid regions. This study investigates the impact of dust events on forest vegetation in Paphos forest in Cyprus, which is a semi-arid area prone to frequent dust storms. Using multispectral and radar satellite data from Sentinel-1 and Landsat series, vegetation responses to eight documented dust events between 2015 and 2019 were analysed, employing BFAST (Breaks For Additive Season and Trend) algorithms to detect abrupt changes in vegetation indices and radar backscatter. The outcomes showed that radar data were particularly effective in identifying only the most significant dust events (PM10 > 100 μg/m3, PM2.5 > 30 μg/m3), indicating that SAR (Synthetic Aperture Radar) is more responsive to pronounced dust deposition, where backscatter changes reflect more substantial vegetation stress. Conversely, optical data were sensitive to a wider range of events, capturing responses even at lower dust concentrations (PM10 > 50 μg/m3, PM2.5 > 20 μg/m3) and detecting minor vegetation stress through indices like SAVI, EVI, and AVI. The analysis highlighted that successful detection relies on multiple factors beyond sensor type, such as rainfall timing and imagery availability close to the dust events. This study highlights the importance of an integrated remote sensing approach for effective forest health monitoring in regions prone to dust events
Translated Cone Exchanges and Invariant Curves
No full textPiecewise isometries are cutting-and-shuffling actions of a metric space, that is, transformations which involve dividing the space into a number of (usually convex) pieces and rearranging each of those pieces according to an isometry. Planar piecewise isometries often appear to display quite complex behaviour despite their lack of hyperbolicity and smoothness. Translated cone exchanges are a class of piecewise isometries on the upper half of the complex plane which involve a partition of this half-plane into cones with a shared vertex at the origin, which are permuted via rotations about the origin and then translated.
In this thesis, we study renormalization and invariant curves in the dynamics of piecewise isometries, focusing on these translated cone exchanges.
We develop methods for visualising the dynamics of piecewise isometries and analysing their geometric structure.
We examine the dynamics of translated cone exchanges at different spatial scales near the real line, in particular proving a form of similarity in the dynamics at arbitrarily small scales which could give rise to an explosion of periodic islands.
We consider a new collection of piecewise-linear invariant curves for some translated cone exchanges, both in terms of the dynamics on the curve as well as the effect of the curves on the dynamics in the surrounding space.
Finally, we develop a formalism for invariant curves for planar piecewise isometries from a planar topological perspective, from which we produce necessary conditions for the existence of such curves as well as a bound on their Hausdorff dimension
Social learning preserves both useful and useless theories by canalizing learners’ exploration
No full textIn many domains, learning from others is crucial for leveraging cumulative cultural knowledge, which encapsulates the efforts of successive generations of innovators. However, anecdotal and experimental evidence suggests that reliance on social information can reduce the exploration of the problem space. Here, we experimentally investigate the extent to which cultural transmission fosters the persistence of arbitrary solutions in a context where participants are incentivized to improve a physical system across multiple trials. Participants were exposed to various theories about the system, ranging from accurate to misleading. Our findings indicate that even under conditions conducive to exploration, the transmission of cultural knowledge canalizes learners’ focus, limiting their consideration of alternative solutions. This effect was observed in both the theories produced and the solutions attempted by participants, irrespective of the accuracy of the provided theories. These results challenge the notion that arbitrary solutions persist only when they are efficient or intuitive and underscore the significant role of cultural transmission in shaping human knowledge and technologies
The role of acoustic telemetry to assess the effects of offshore wind infrastructure on fish behaviour, populations and predation
No full textInshore and offshore coastal regions are becoming increasingly occupied by anthropogenic infrastructure. This trend will continue with the drive for offshore renewable energy development to reduce carbon emissions and provide energy security. The introduction of structures to the marine environment can have direct and indirect effects on benthic and pelagic habitats, and subsequent impacts on species contributing to these ecosystems. Fish are both prey and predators and, therefore, important components to the functioning of food webs in these environments. Should their behaviour, distribution and/or populations be altered by introduced structures then it is important to understand the direction and magnitude of effects, both at local and regional seascape scales, to understand how these effects may influence ecological interactions. The migratory behaviour of some fish species also contributes temporal and spatial variability and uncertainty to observed patterns, which should be characterised to provide a fuller understanding of the consequences of introduced structures. Acoustic telemetry provides insights into the movement and behaviour of individual fish at scales from single wind turbines to regional networks of offshore wind farm developments. Here we review how acoustic telemetry has added to the understanding of fish behaviour around introduced structures and discuss how its use can be (and is being) expanded to provide a wider ecological understanding of the impacts of offshore wind farms through collaborative networks, and integrated research techniques and analyses
The elastic ruler: Placebo responses, clinical trials, and medical knowledge
No full textThis paper first poses a skeptical challenge to clinical trials in medicine. The efficacy of treatments is measured against placebo; but placebo responses are not constant. They fluctuate with demographic variables, and they seem to be increasing over time. We therefore find ourselves measuring with the equivalent of what Wittgenstein termed an “elastic ruler”.
I then propose a “skeptical solution” to the problem. Elastic rulers are suitable tools for measuring dynamic, floating networks of values, like foreign currency exchanges. We can assuage the skeptical concerns by understanding clinical trials in this way; I suggest several practical guidelines for doing so
Aligning strategic and participatory approaches to agri-environment scheme design and implementation to enhance nature recovery outcomes
No full textNature recovery requires the provisioning of resources in the right place and in sufficient quantities to support wildlife populations and improve ecological processes. Agri-environment schemes (AES) have been a major mechanism for delivering environmental management across EU farmed landscapes, but measured benefits to nature are often negligible in large part due to a lack of strategic spatial targeting of management actions. As an example, AES in England are often delivered using a participatory strategy, typically at individual farm scale, with types of management agreements and uptake reflecting the business model and interests of each farm. However, this implementation model can result in poorly distributed conservation resources and, consequently, a failure to recover nature across larger scales, even if individual agreements are delivered well. Achieving effective, large-scale nature recovery through AES requires aligning its implementation with spatially targeted approaches that prioritise specific conservation goals. We discuss the rationale for, and major barriers to, aligning AES design and implementation to these approaches. We then highlight how, through the framework of systematic conservation planning, both the strategic and participatory components of AES could be aligned better to enhance nature recovery outcomes. To ensure AES help achieve nature recovery goals, clear and measurable targets must be set with the type and spatial configuration of actions designed to enable meeting targets. Strategic spatial targeting must also be carried out with the implementation phase in mind, accounting for socio-economic opportunities and barriers to engagement and acknowledging that uncertainties around farm-scale implementation means plans must be adaptable. Participatory approaches for AES design and implementation that support delivery of spatially targeted management actions are required, most notably by facilitating collaboration or cooperation across farm holdings. For AES to contribute effectively to nature recovery goals, aligning strategic and participatory approaches in its design and implementation is crucial. This requires uniting knowledge across disciplines and cultures and ensuring that information is shared to support progressive refinement of scheme design and guidance towards achieving overall nature recovery goals
Enhancing Resilience of Intermittent Water Supply Systems to Power Outages
No full textAn estimated 1.3 billion people in South Asia, Latin America, and Africa receive water for domestic purposes through piped networks for limited periods, referred to as intermittent water supply (IWS). Electricity intermittency is one of the main causes of water supply intermittency. In water supply systems (WSSs), electrical power is used for pumping water from the sources to the treatment plants and then to users via the water distribution systems (WDSs). If the electrical power system fails to supply at WDSs pumping stations, this will lead to failure in water distribution systems. To ensure more sustainable IWS systems, evaluating and enhancing water infrastructure resilience is crucial. Understanding the underlying system’s inherent resilience is a prerequisite for enhancing its resilience. This study presents a novel approach for investigating the performance of an IWS system under power outage (modelled as pump failure) scenarios and identifying potential intervention strategies to enhance network resilience to limited power availability. The proposed methodology employs a two-step strategy: in the first step a global resilience analysis (GRA) approach is used to investigate the performance of an IWS system under pump failure scenarios to identify and localize its main vulnerabilities. In the second step optimum adaptation intervention strategies are identified by the application of the evolutionary multiobjective optimization method. A nondominated sorting genetic algorithm (NSGA-II) is used for the optimum operation and rehabilitation of IWS systems considering three objectives: the operation and rehabilitation costs, the level of equity, and the proportion of effective supplied hours. The results show that while the adaptation strategy of optimal operation intervention improved equity and effective supply hours slightly, the adaptation strategies of optimum operation and rehabilitation intervention significantly increased the system resilience to power outage/pump failure scenarios by improving both equity and effective supply hours
War fatalities in Russia in 2022–2023 estimated via excess male mortality: a research note
No full textIn this research note, we used excess deaths among young males to estimate the number
of Russian fatalities in the Russo-Ukrainian war in 2022–23. We based our calculations on
the official mortality statistics, split by age and gender. To separate excess deaths due to war
from those due to Covid-19, we relied on the ratio of male to female deaths, and extrapolated
the 2015–19 trend to get the baseline value for 2022–23. We found noticeable excess male
mortality in all age groups between 15 and 49, with 58 500 ± 2 500 excess male deaths in 2022–
23 (20 600 ± 1 400 in 2022 and 37 900 ± 1 500 in 2023). These estimates were obtained after
excluding all HIV deaths that showed complex dynamics unrelated to the war. Depending on
the modelling assumptions, the estimated number of deaths over the two years varied from
about 46 600 to about 64 100, with 58 500 corresponding to our preferred model. Our estimate
should be treated as a lower bound on the true number of deaths as the data do not include
either the Russian military personnel missing in action and not officially declared dead, or the
deaths registered in the Ukrainian territories annexed in 2022
