A New Mechanism for Generation of Langmuir Circulations

A new mechanism has been identified that explains the generation of Langmuir circulations. A wind-driven current in the presence of surface waves gives rise to an instability where the emerging circulations redistribute the turbulence in the cross-wind direction. The non-uniform eddy-viscosity locally changes the rate of momentum transfer from the wind to the shear current, producing a non-uniform velocity field. The interaction of this non-uniform velocity field with the surface waves, due to the Craik-Leibovich vortex force, amplifies the circulations and creates a feedback mechanism. The currently accepted CL2 model of instability assumes a constant eddy-viscosity. This paper presents a model which explains the generation of Langmuir circulations and its predictions of both spatial and time scales are in good agreement with experimental results. The modeling approach combines a perturbation method with a RANS turbulence model. Through parametric variation of the perturbation, the growth rate and spatial scales of the circulations are extracted from the simulations

An optimisation model for scheduling the decommissioning of an offshore wind farm

An optimisation model is proposed for scheduling the decommissioning of an offshore wind farm in order to minimise the total cost which is comprised of jack-up vessel, barge (transfer) vessel, inventory, processing and on-land transportation costs. This paper also presents a comprehensive review of the strategic issues relating to the decommissioning process and of scheduling models that have been applied to offshore wind farms. A mathematical model using integer linear programming is developed to determine the optimal schedule considering several constraints such as the availability of vessels and planning delays. As the decommissioning problem is challenging to solve, a matheuristic approach based on the hybridisation of a heuristic approach and an exact method is also proposed to find near optimal solutions for a test set of problems. A set of computational experiments has been carried out to assess the proposed approach

A decision support system for strategic maintenance planning in offshore wind farms

This paper presents a Decision Support System (DSS) for maintenance cost optimisation at an Offshore Wind Farm (OWF). The DSS is designed for use by multiple stakeholders in the OWF sector with the overall goal of informing maintenance strategy and hence reducing overall lifecycle maintenance costs at the OWF. Two optimisation models underpin the DSS. The first is a deterministic model that is intended for use by stakeholders with access to accurate failure rate data. The second is a stochastic model that is intended for use by stakeholders who have less certainty about failure rates. Solutions of both models are presented using a UK OWF that is in construction as an example. Conclusions as to the value of failure rate data are drawn by comparing the results of the two models. Sensitivity analysis is undertaken with respect to the turbine failure rate frequency and number of turbines at the site, with near linear trends observed for both factors. Finally, overall conclusions are drawn in the context of maintenance planning in the OWF sector

A deep learning-based approach to diagnose mild traumatic brain injury using audio classification

Mild traumatic brain injury (mTBI or concussion) is receiving increased attention due to the incidence in contact sports and limitations with subjective (pen and paper) diagnostic approaches. If an mTBI is undiagnosed and the athlete prematurely returns to play, it can result in serious short-term and/or long-term health complications. This demonstrates the importance of providing more reliable mTBI diagnostic tools to mitigate misdiagnosis. Accordingly, there is a need to develop reliable and efficient objective approaches with computationally robust diagnostic methods. Here in this pilot study, we propose the extraction of Mel Frequency Cepstral Coefficient (MFCC) features from audio recordings of speech that were collected from athletes engaging in rugby union who were diagnosed with an mTBI or not. These features were trained on our novel particle swarm optimised (PSO) bidirectional long short-term memory attention (Bi-LSTM-A) deep learning model. Little-to-no overfitting occurred during the training process, indicating strong reliability of the approach regarding the current test dataset classification results and future test data. Sensitivity and specificity to distinguish those with an mTBI were 94.7% and 86.2%, respectively, with an AUROC score of 0.904. This indicates a strong potential for the deep learning approach, with future improvements in classification results relying on more participant data and further innovations to the Bi-LSTM-A model to fully establish this approach as a pragmatic mTBI diagnostic tool

How landscapes remember

This paper considers the possibility that as subject or agent, the landscape might have the potential to contain, store or transmit memories of their past, which are engaged experientially as uncanny. In a simple sense it asks why there are some landscapes – or landscape features – that are regarded as spiritually animated by different social groups, at different times. The paper focuses on the Neolithic temple site of Borġ-in-Nadur, in Southern Malta, which as well as having been a site of prehistoric ritual activity has more recently been the site of a significant devotion to the Virgin Mary, who graced the site with regular apparitions, and a focus for national and transnational Goddess pilgrimage. The paper suggests that sites such as Borġ-in-Nadur can be seen as palimpsest landscapes, in which memory is layered such that experiential engagements with them draw the past in to the present, and forwards into the future. The paper examines the intertwining of prehistoric, Catholic and Neo-pagan engagements with Borġ-in-Nadur, extending Pierre Nora’s concept of lieux de memoire (sites of memory) to encompass the milieux de memoire, or memorial environments, which are themselves also context of, and for, the uncanny

Early Cretaceous vegetation and climate change at high latitude: Palynological evidence from Isachsen Formation, Arctic Canada

Quantitative palynology of the marginal marine and deltaic-fluvial Isachsen Formation of the Sverdrup Basin, Canadian Arctic, provides insight into high latitude climate during much of the Early Cretaceous (Valanginian to early Aptian). Detrended Correspondence Analysis of main pollen and spore taxa is used to derive three ecological groupings influenced by moisture and disturbance based on the botanical affinities of palynomorphs: 1) a mixed coniferous assemblage containing both lowland and upland components; 2) a conifer-filicopsid community that likely grew in dynamic lowland habitats; and, 3) a mature dry lowland community composed of Cheirolepidiaceans. Stratigraphic changes in the relative abundance of pollen and spore taxa reflect climate variability in this polar region during the ~20 Mya history of the Isachsen Formation. The late Valanginian was relatively cool and moist and promoted lowland conifer-filicopsid communities. Warming in the Hauterivian resulted in the expansion coniferous communities in well-drained or arid hinterlands. A return to relatively cool and moist conditions in the Barremian resulted in the expansion of mixed lowland communities. This work demonstrates the utility of a multivariate statistical approach to palynology to provide insight into the composition and dynamics of ecosystems and climate of high latitude regions during the Early Cretaceous

Contextualizing climate justice activism: knowledge, emotions, motivations, and actions among climate strikers in six cities

In August 2018, Swedish teenager Greta Thunberg started to strike from school on Fridays to protest against a lack of action on the climate crisis. Her actions sparked a historically large youth movement, leading to a series of school strikes across the world. Over the course of one week in September 2019, striking school children, students and other grassroots movements, such as Extinction Rebellion, called for everyone to participate in a global Climate Strike. This paper is based on comparative research with climate protesters in six cities: Brighton and London (United Kingdom), Montreal (Canada), New Haven and New York (USA), and Stavanger (Norway). Based on original interviews with 64 protesters, the study examines their knowledge, emotions, motivations, and actions in relation to climate change, including any lifestyle changes they have undertaken before or after their protests. Our findings show that protesters have varying degrees of knowledge about climate change, and have taken a range of actions in their own lives to address climate change. They also manifest a wide spectrum of emotions about climate change, and different motivations for taking part in climate strikes. These features are under-studied and dynamically evolving at the present conjuncture. On this basis, we call for expanded academic attention to human, emotional, epistemic, and seemingly mundane aspects of climate protests, their structural tendencies and relational expressions, and the implications for our ability to address underlying drivers

Trends of Pathogen Overload and the Influence on Social Behavior

A review of the literature has been undertaken showing that higher levels of pathogen stress have been positively correlated with multiple aspects of social structure: non-sororal polygyny (Ember et al. 2007; Low 1990), exogamy and bride capture (Low 1990), resource defense (Barber 2008; Hames 1996), and male-female body alteration (Singh and Bronstad 1997). Non-sororal polygyny is the most effective reproductive strategy to defend against pathogen stress, as it promotes much genetic variability within gene pools, allowing for more pathogenic resistance in individuals because of heterozygous al/eles. In order to secure mates while faced with ecological extremes, individuals will modify their bodies to increase the attractiveness, an indicator of pathogen resistance (Low 1990; Gangestad and Buss 1993). Intrasocietal data are needed to test the direct relations between pathogenically debilitated individuals and likelihood of obtaining a mate (Low 1990). Intra-societal data are also needed to test the direct relations between pathogenically debilitated individuals and intensity of body modification (Singh and Bronstad 1997)