346 research outputs found

    Capillary-Gravity Waves on Depth-Dependent Currents: Consequences for the Wave Resistance

    Full text link
    We study theoretically the capillary-gravity waves created at the water-air interface by a small two-dimensional perturbation when a depth-dependent current is initially present in the fluid. Assuming linear wave theory, we derive a general expression of the wave resistance experienced by the perturbation as a function of the current profile in the case of an inviscid fluid. We then analyze and discuss in details the behavior of the wave resistance in the particular case of a linear current, a valid approximation for some wind generated currents.Comment: Submitted to EP

    Feasting and mobility in Iron Age Ireland: multi-isotope analysis reveals the vast catchment of Navan Fort, Ulster

    Get PDF
    Navan Fort is an iconic prehistoric Irish ceremonial centre and the legendary capital of Ulster. The fort has produced an exceptional pig-dominated faunal assemblage that also contained a barbary macaque skull. Dating from the 4th to 1st century BC, it is likely to be a ceremonial feasting centre that may have drawn people and their animals from across Ulster and beyond. This study uses a multi-isotope (87Sr/86Sr, δ34S, δ13C, δ15N) approach to identify non-local animals and reconstruct site catchment. New biosphere mapping means that isotope data can be more confidently interpreted and the combination of strontium and sulphur analysis has the potential to estimate origins. In the absence of human remains, fauna provide the best proxy for human movement. Results for the 35 analysed animals are wide-ranging, especially in terms of strontium (0.707–0.715), which has the largest range for an Irish site. Sulphur values are more restricted (13.1‰−17.1‰) but are high in the context of British and Irish data. Results provide clear evidence for animals (and thus people) coming from across Ulster and beyond, demonstrating the site’s wide catchment. Navan Fort was clearly a major ceremonial centre with far-reaching influence and hosted feasts that drew people and animals from afar

    The Influence of Personality, Safety Attitudes, and Risk Perception of Pilots: A Modeling and Mediation Perspective

    Get PDF
    Objective: The purpose of the current study was to assess the influence of personality traits on safety attitudes and risk perceptions. Background: The ability to accurately assess risk remains a focal point of aviation training. This research seeks to understand if safety attitudes serve as a mediator. Method: Using a sample of 2,857 pilots, a statistical model was created through two independent stages. In stage 1, approximately 50% of the data were used to create the model using structural equation modeling techniques, and in stage 2, the model was independently validated. Results: The findings indicated that personality factors positively influenced risk perception, whereas personality increased, so did the pilot\u27s perception of the risk level. Self-confidence was negatively related to risk perceptions, indicating that a pilot\u27s self-confidence increases their perception of risk decreases. Additionally, self-confidence was a significant mediator to the relationship between personality factors and risk perception. Conclusion: The original scales had some validity issues, but the re-specified model provided some meaningful findings, especially in the relationships between personality traits, self-confidence, and risk perception. The model explained 26.4% of the variance in self-confidence and 9.5% of risk perception variance. Application: The findings highlight the importance for pilots to be aware of how increased self-confidence may influence their perceptions of risk. As pilots gain experience and self-confidence, care needs to be given to ensure greater risks are not taken, offsetting the value of the experience and self-confidence

    Feeding the Roman army in Britain

    Get PDF
    How did the Roman Empire supply and maintain its frontier garrisons? What was the impact on populations and landscapes of conquered territories? The Feeding the Roman Army in Britain project will answer these questions by establishing how soldiers were provisioned and how frontiers operated as economic as well as militarised zones

    Understanding Middle Neolithic food and farming in and around the Stonehenge World Heritage Site: an integrated approach

    Get PDF
    Little synthesis of evidence for Middle Neolithic food and farming in Wiltshire, particularly in and around the Stonehenge World Heritage Site (WHS) has been possible, until now, due to a paucity of assemblages. The excavation of a cluster of five Middle Neolithic pits and an inhumation burial at West Amesbury Farm (WAF) has prompted a review of our understanding of pit sites of this period from the county. Bioarchaeological assemblages are used to investigate evidence for the consumption of animal and plant-based foods, and for agricultural and pastoral farming. For the first time Middle Neolithic zooarchaeological evidence, including strontium isotope data, is considered alongside archaeobotanical data, and radiocarbon dating. The absence of cultivated plants from WAF and contemporary sites in the county is consistent with the hypothesis that the reduction in cereal cultivation and greater reliance of wild plants witnessed in the later part of the Neolithic in southern England began in the Middle Neolithic. The zooarchaeological evidence from the same sites demonstrates that the shift away from cereal cultivation may be concurrent with, rather than earlier than, an increase in the relative proportion of deposited pig bones relative to cattle. Both cattle and pigs deposited in pits at WAF have strontium and sulphur isotope values consistent with the local biosphere, and therefore were potentially raised in the area. Zooarchaeological data from WAF compliments that from human dental calculus and lipid residues in associated Peterborough Ware pottery that local cattle husbandry included exploitation of dairy. It also highlights the presence of consistent food preparation methods between pits as seen through butchery practice. The faunal and archaeobotanical remains from contemporary pit deposits suggest that similar farming and subsistence strategies can be proposed across the county, though with some inter-site variation in deposition. Together these excavated pit sites are likely to represent only a sample of those present in the area. Application of a similar integrated approach to material from other Middle Neolithic pits holds potential for better understanding of food and farming in this previously neglected period