Open Research Exeter - University of Exeter
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Safety of embodied navigation: A survey
No full textAs large language models (LLMs) continue to advance and gain influence, the development of embodied AI has accelerated, drawing significant attention, particularly in navigation scenarios. Embodied navigation requires an agent to perceive, interact with, and adapt to its environment while moving toward a specified target in unfamiliar settings. However, the integration of embodied navigation into critical applications raises substantial safety concerns. Given their deployment in dynamic, real-world environments, ensuring the safety of such systems is critical. This survey provides a comprehensive analysis of safety in embodied navigation from multiple perspectives, encompassing attack strategies, defense mechanisms, and evaluation methodologies. Beyond conducting a comprehensive examination of existing safety challenges, mitigation technologies, and various datasets and metrics that assess effectiveness and robustness, we explore unresolved issues and future research directions in embodied navigation safety. These include potential attack methods, mitigation strategies, more reliable evaluation techniques, and the implementation of verification frameworks. By addressing these critical gaps, this survey aims to provide valuable insights that can guide future research toward the development of safer and more reliable embodied navigation systems. Furthermore, the findings of this study have broader implications for enhancing societal safety and increasing industrial efficiency.</p
A framework for assessing global health impacts of polar change: An urgent call for interdisciplinary research.
No full textResearch on the human health risks of climate change is expanding, yet the influence of polar region shifts on these risks remains underexplored. This paper presents a framework to assess global and regional health risks stemming from polar physical changes. The polar regions are experiencing rapid environmental transformations, including melting ice, ocean warming, ocean acidification, permafrost thaw, intensifying wildfires, and alterations to jet streams, ocean currents. These changes can amplify global risks, affecting human health even in distant regions. The paper identifies potential cascading impacts on health and well-being via drivers such as extreme weather, heat stress, air, water quality, food supply, safety, vector ecology, and sea-level rise. A scoping review was conducted by an international team of public health and polar experts to support thematic categorization of regional and global health risks. The paper advocates integrating these amplified risks into health impact assessments through interdisciplinary, international collaboration to inform future policy responses.</p
European native oyster reef ecosystems are universally collapsed
No full textOyster reefs are often referred to as the temperate functional equivalent of coral reefs. Yet evidence for this analogy was lacking for the European native species Ostrea edulis. Historical data provide a unique opportunity to develop a robust definition for this ecosystem type, confirm that O. edulis are large-scale biogenic reef builders, and assess its current conservation status. Today, O. edulis occur as scattered individuals or, rarely, as dense clumps over a few m2. Yet historically, O. edulis reef ecosystems persisted at large scales (several km2), with individual reefs within the ecosystems present at the scale of several hectares. Using the IUCN Red List of Ecosystems Framework, we conclude the European native oyster reef ecosystem type is collapsed under three of five criteria (A: reduction in geographic distribution, B: restricted geographic range, and D: disruption of biotic processes and interactions). Criterion C (environmental degradation) was data deficient, and Criterion E (quantitative risk analysis) was not completed as the ecosystem was already deemed collapsed. Our assessment has important implications for conservation policy and action, highlighting that the habitat definitions on which conservation policies are currently based reflect a highly shifted baseline, and that the scale of current restoration efforts falls far short of what is necessary for ecosystem recovery.</p
Correction of coupled aerodynamic loads in high-frequency force-balance testing using a Bayesian approach
No full textHigh-frequency force-balance testing is one of the most practical approaches for evaluating wind loads and wind-induced responses on high-rise buildings in wind tunnels. However, the method is susceptible to measurement bias caused by resonant amplification and modal coupling between the balance and the structural model. Traditional correction methods partly mitigate resonant amplification but remain limited under modal coupling, particularly in cases of closely spaced modes. This study presents a physically grounded correction framework based on Bayesian operational modal analysis, which incorporates the coupled dynamic characteristics of the balance model system (BMS) into a Bayesian inference scheme, enabling statistically consistent and physically interpretable identification of its modal characteristics. By leveraging the identified modal parameters of the BMS, the method decouples aerodynamic loads, suppresses dynamic amplification, and reconstructs bias-reduced aerodynamic load spectra. Numerical simulations demonstrate the robustness of the method under varying modal proximity and coupling, while wind-tunnel experiments on a supertall building model further validate its effectiveness. The results highlight the potential of the proposed framework to improve aerodynamic-load correction and structural-response prediction in wind-tunnel testing</p
On the distribution of certain arithmetic functions
No full textIn this dissertation, we investigate exponential sums of the form
\begin{align*}
S_f(N;\Theta)=\sum_{n\leq N}f(n)e(n\Theta),
\end{align*}
where , and is either a strongly additive function subject to certain restrictions or the indicator function of the semiprimes. To obtain non-trivial estimates on the minor arcs for with strongly additive coefficients, we employ a classical result of Montgomery and Vaughan. In the case where is the indicator function of the semiprimes, we provide two distinct proofs. The first one introduces a new approach based on the Dirichlet hyperbola method, for which we establish generalised Vinogradov's lemma. The second proof offers an alternative argument for the Weyl sum
\begin{align*}
\sum_{n\leq N}\Lambda_2(n)e(n\Theta),
\end{align*}
where denotes the generalised Von Mangoldt function, by deriving and employing generalised Vaughan's identity.
We have also studied the asymptotic behaviour of the weighted partition function , defined by the generating series
\begin{align*}
1+\sum_{n=1}^{\infty}p_f(n)z^n
=\prod_{m=1}^{\infty}(1-z^n)^{-f(n)}\quad (|z|<1).
\end{align*}
Here is taken to be either a real, positive-valued strongly additive function with certain restrictions, or the indicator function of the semiprimes. To obtain asymptotic estimates, we employ the saddle-point method, which may be viewed as a coarse version of the Hardy-Littlewood circle method. The main difficulty in analysing for these choices of weight functions lies in the behaviour of the associated Dirichlet series
\begin{align*}
\sum_{n=1}^{\infty}\frac{f(n)}{n^s},\quad\mathrm{Re}(s)>\alpha;\;\alpha\in\mathbb{R},
\end{align*}
which plays a central role in the estimation of the major arcs. In the case where is strongly additive, the above Dirichlet series does not have an Euler product. Thus, determining its analytic properties, such as the poles and residues poses greater challenges. When is taken to be the indicator function of the semiprimes, the Dirichlet series reduces to the square of the prime zeta function , where .
Analysing the behaviour of requires careful treatment of its logarithmic branches, which adds a distinctive difficulty to these types of weighted partition problems. Finally, we have concluded by remaking a result on the probabilistic distribution of weighted partition functions.</p
BIOPOLE - Biogeochemical processes and ecosystem functioning in changing polar systems and their global impacts
No full textThe export of elements (particularly carbon, nitrogen and phosphorus) from the Poles critically supports global marine biodiversity and major fisheries as well as the sequestration of atmospheric carbon to the deep ocean. Ecosystem processes regulate this export, but major uncertainties remain in terms of how and by how much. Progress on understanding key ecosystem interactions is hindered by lack of data and their representation in Earth system models is poor. The two polar regions share similarities in environmental extremes which make them sensitive to the impacts of climate change. They both receive nutrients from multiple and diverse sources and the delivery of these nutrients to other oceans is regulated by similar ecosystem processes. However, the extent to which these ecosystem processes will be modified by climate change is unclear and urgently needs to be determined. BIOPOLE will determine how polar ecosystems regulate the balance of carbon and nutrients in the world’s oceans and, through it, their effect on global fish stocks and carbon storage. It will address this challenge by integrating ambitious fieldwork campaigns and innovative modelling in a multidisciplinary and highly coordinated approach. BIOPOLE will capitalise on world-leading capabilities and infrastructure in ocean and high-latitude research, including cutting-edge land-based facilities, state-of-the-art polar research vessels and innovative autonomous instrumentation. Collaboration with national and international partners will further strengthen BIOPOLE’s multidisciplinary approach and efficient use of infrastructure. BIOPOLE’s legacy will be the first assessment of the global impact of polar ecosystems on biogeochemical cycling and fish stocks; technologically-novel approaches and strong partnerships between leading international science groups.</p
Compressive behaviour of mortar panels reinforced with polymeric auxetic lattices: Experimental testing and numerical modelling
No full textThis paper examines the compressive performance of composite cement-based mortar panels embedding polymeric auxetic lattices, through both experimental testing and numerical modelling. In the experimental phase, lattices measuring 200 mm × 200 mm × 30 mm are fabricated using three-dimensional (3D) printing technology with Polyethylene Terephthalate Glycol (PETG) in four different auxetic geometries: re-entrant, tetra-anti-chiral, missing rib, and double arrowhead. Plain mortar specimens (panels) and those embedded with conventional non-auxetic honeycomb (hexagonal) lattices are prepared and tested to provide a comparative baseline against the mortar-filled auxetic lattices. The test results reveal that the auxetic reinforcing lattices significantly enhance the compressive characteristics of the mortar panels. On average, the peak load, toughness, and ductility ratio increase by 10 %, 1400 %, and 170 %, respectively; however, the initial stiffness is reduced by about 50 % compared to the plain mortar counterparts. A Finite Element (FE) model is developed and validated against the experimental data. The model is then employed as a virtual laboratory unit to investigate the performance of various Lattice-Reinforced Cementitious Composite (LRCC) panels with conventional construction materials (steel and normal-strength concrete).</p
Estimating coral reef carbonate budgets using Structure-from-Motion photogrammetry
No full textCarbonate budget assessments quantify rates of calcium carbonate production and erosion from habitat-altering marine taxa and can be used to evaluate the potential for reef growth and the persistence of coral reef frameworks. Tracking the key ecosystem processes that control carbonate budgets is increasingly critical as climate change threatens to shift reefs toward net erosional states. However, the complex and time-intensive nature of traditional in-water carbonate budget surveys have limited their application in logistically challenging locations. Here, we introduce a new field-efficient methodology for collecting benthic carbonate production, endolithic bioerosion, and urchin erosion data for census-based carbonate budget assessments using Structure-from-Motion (SfM) photogrammetry. To evaluate the efficacy of our approach, we compared SfM-derived metrics with in-water data collected following the ReefBudget methodology at sites in the main Hawaiian Islands, Mariana Archipelago, and American Samoa. Our image-based SfM approach generated gross carbonate production, urchin erosion, and net carbonate production rates that were comparable to in-water estimates while still capturing site-level variability in production states. We observed greater deviation between methods in several constituent metrics, as SfM estimates of rugosity and endolithic bioerosion were higher and coral cover and urchin densities lower than in-water data; yet, these differences did not ultimately result in major systematic methodological biases in net production across our sites. Although SfM techniques can require significant upfront costs and annotation time, they also offer substantial advantages over in-water surveys. These advantages extend across field efficiency, measurement precision for key parameters, scalability, and potential to leverage models for multiple applications.</p
Trade Misinvoicing: Corruption and Economic Performance in Africa
No full textThis paper analyses how trade misinvoicing, as a direct measure of corruption, affects the eco?nomic performance of Africa, given that most of the existing studies on the corruption-economy nexus are based on corruption perception index, world governance indicators, international coun?try risk guide, and other corruption indices. Using GMM and OLS econometric techniques on a sample of 35 African countries from 2008 to 2017, our results show that corruption, as measured by value gap reduces income per capita in the selected African countries. Specifically, a 1 percent increase in the value gap will reduce GDP per capita by 0.309-0.414 percent. The results also show that trade mispricing is positively associated with tariffs. Concerning the control variables, tariffs and external debts have a negative association with national income, as expected. This result survives a robustness check of partner-country trade data sourced from UN Comtrade, a sub-sample of the value gap, and using the CPI measure of corruption. The policy recommen?dation of this study is to strengthen the regulatory framework for the collection of tariffs and to close any gaps in the reporting of trade data in the selected African countries.</p
Quantifying coral reef accretion in a changing world: approaches, challenges and emerging opportunities
No full textThe long-term development of coral reef frameworks and the net vertical accretion of reefs fundamentally underpins the provisioning of most reef-related ecosystem services. One area of particular concern at present is how rates of reef accretion are changing under ecological decline and what the consequences of this may be for the capacity of reefs to keep pace with near-future sea-level rise (SLR). This may have major implications for the capacity of reefs to maintain their coastal protective functions and to support reef island stability. Both are issues relevant to understanding future tropical coastal risk. Long-term (millennial timescale) rates of reef accretion are relatively well constrained, including through past periods of sea-level fluctuations. However, widespread and persistent ecological degradation of coral communities has caused many reefs to diverge significantly from their past accretion trajectories. This renders historical analogues increasingly unreliable for projecting future accretion potential. Addressing this necessitates a reorientation towards considering reef accretion rates across shorter (ecological to geomorphic) timescales, i.e., over years to multi-decades. This is essential if we are to better constrain contemporary reef accretion rate and SLR interactions at timescales relevant to predicting emerging coastal risks and understanding future implications for reef-derived benefits. Here, we review existing approaches for quantifying vertical reef accretion rates of modern reefs. These methods span data recovered from fossil outcrops or core-derived records, the conversion of carbonate budget data, direct in situ measurements and emerging remote sensing and image-based techniques. The review explores the advantages and limitations of these different approaches and outlines options for developing an integrated framework to link past, present and future reef accretion potential.</p