267,508 research outputs found

    What KUBIS did: creating educational space for small and medium-sized enterprises

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    Foreword

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    Observations of clustering inside oceanic bubble clouds and the effect on short-range acoustic propagation

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    It has recently been shown [Weber, T. C. et al. (Year: 2007). “Acoustic propagation through clustered bubble clouds,” IEEE J. Ocean. Eng.32, 513–523] that gas bubble clustering plays a role in determining the acoustic field characteristics of bubbly fluids. In particular, it has been shown that clustering changes the bubble-induced attenuation as well as the ping-to-ping variability in the acoustic field. The degree to which bubble clustering exists in nature, however, is unknown. This paper describes a method for quantifying bubble clustering using a high frequency (400kHz) multibeam sonar, and reports on observations of near-surface bubbleclustering during a storm ( 14.6m∕s wind speed) in the Gulf of Maine. The multibeam sonardata are analyzed to estimate the pair correlation function, a measure of bubble clustering. In order to account for clustering in the mean acoustic field, a modification to the effective mediumwave number is made. With this modification, the multibeam sonar observations are used to predict the effect of clustering on the attenuation of the mean field for short-range propagation (1 m) at frequencies between 10 and 350kHz . Results for this specific case show that clusteringcan cause the attenuation to change by 20%–80% over this frequency range

    A revision of Pediacus Shuckard (Coleoptera: Cucujidae) for America north of Mexico : with notes on other species

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    The genus Pediacus Shuckard is revised for America north of Mexico. Seven species are recorded: P. andrewsi Thomas, n. sp.; P. fuscus Erichson; P. gracilis Thomas, n. sp.; P. hesperoglaber Thomas, n. sp.; P. ommatodon Thomas, n. sp.; P. stephani Thomas, n. sp.; and P. subglaber LeConte, new status. The species are described and illustrated, and a key is presented for their identification. The described European and Neotropical species are reviewed and illustrated

    On Gaussian Random Supergravity

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    We study the distribution of metastable vacua and the likelihood of slow roll inflation in high dimensional random landscapes. We consider two examples of landscapes: a Gaussian random potential and an effective supergravity potential defined via a Gaussian random superpotential and a trivial K\"ahler potential. To examine these landscapes we introduce a random matrix model that describes the correlations between various derivatives and we propose an efficient algorithm that allows for a numerical study of high dimensional random fields. Using these novel tools, we find that the vast majority of metastable critical points in NN dimensional random supergravities are either approximately supersymmetric with FMsusy|F|\ll M_{\text{susy}} or supersymmetric. Such approximately supersymmetric points are dynamical attractors in the landscape and the probability that a randomly chosen critical point is metastable scales as log(P)N\log(P)\propto -N. We argue that random supergravities lead to potentially interesting inflationary dynamics.Comment: 36 pages, 9 figure
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