37 research outputs found

    Cavitation noise scaling. Status based on NATO RSG. Part 1. Survey of the problems in cavitation noise scaling and prediction

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    Paper presents a status report on cavitation noise scaling based on work done by a relevant Nato Research Study Group (RSG). The RSG 3 was expected to find out how to improve reliability in predicting cavitation noise from model testing, and how to equalize this reliability for the various model test facilities in use

    Voraussage von Geräuschen der Propellerkavitation aus Modellversuchen

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    Nach einigen Anmerkungen über Kavitationsgeräusch folgt ein Überblick über die Probleme, die mit der i.T. genannten Aufgabe verbunden sind. Am Ende wird skizziert, wie weit man heute in der Lage ist, Kavitationsgeräusch aus Modellversuchen vorherzusagen

    Climate-averaging of terrestrial faunas: an example from the Plio-Pleistocene of South Africa

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    Fundamental to the interpretation of bone-bearing faunal deposits is an understanding of the taphonomic processes that have modified the once living fossil community. An often neglected source of bias is that of climate-averaging, which occurs when the duration of bone accumulation exceeds the duration of an individual climatic episode. Tropical and subtropical climate change is dominated by precessional cyclicity (~21,000 year cycle), which controls monsoon rainfall intensity and thus plant communities over time. Under a climate-averaging scenario, the paleoecological characteristics of a faunal deposit represent an amalgamation of more than one phase of the precessional cycle. We investigate the degree of climate-averaging in Plio-Pleistocene bone breccias from South Africa by comparing stable isotope measurements of fossil enamel with the evidence from high-resolution speleothem paleoclimate proxies. We conclude that each of the four faunal assemblages studied are climate-averaged, having formed over a time period in excess of one-third of a precessional cycle (~7000 years). This has implications for the reconstruction of hominin paleoenvironments and estimates of Plio-Pleistocene biodiversity. We hypothesize that climate-averaging may be a common feature of tropical terrestrial vertebrate assemblages throughout the Cenozoic and Mesozoic
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