23,906 research outputs found

    Global distribution of modern shallow marine shorelines. Implications for exploration and reservoir analogue studies

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    Acknowledgments Support for this work came from the SAFARI consortium which was funded by Bayern Gas, ConocoPhillips, Dana Petroleum, Dong Energy, Eni Norge, GDF Suez, Idemitsu, Lundin, Noreco, OMV, Repsol, Rocksource, RWE, Statoil, Suncor, Total, PDO, VNG and the Norwegian Petroleum Directorate (NPD). This manuscript has benefited from discussion with Bruce Ainsworth, Rachel Nanson and Christian Haug Eide. Boyan Vakarelov and Richard Davis Jr. are thanked for their constructive reviews and valuable comments that helped to improve the manuscript.Peer reviewedPostprin

    Efficient high-dimensional entanglement imaging with a compressive sensing, double-pixel camera

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    We implement a double-pixel, compressive sensing camera to efficiently characterize, at high resolution, the spatially entangled fields produced by spontaneous parametric downconversion. This technique leverages sparsity in spatial correlations between entangled photons to improve acquisition times over raster-scanning by a scaling factor up to n^2/log(n) for n-dimensional images. We image at resolutions up to 1024 dimensions per detector and demonstrate a channel capacity of 8.4 bits per photon. By comparing the classical mutual information in conjugate bases, we violate an entropic Einstein-Podolsky-Rosen separability criterion for all measured resolutions. More broadly, our result indicates compressive sensing can be especially effective for higher-order measurements on correlated systems.Comment: 10 pages, 7 figure

    Intermittency in the transition to turbulence

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    It is commonly known that the intermittent transition from laminar to turbulent flow in pipes occurs because, at intermediate values of a prescribed pressure drop, a purely laminar flow offers too little resistance, but a fully turbulent one offers too much. We propose a phenomenological model of the flow, which is able to explain this in a quantitative way through a hysteretic transition between laminar and turbulent states, characterized by a disturbance amplitude variable that satisfies a natural type of evolution equation. The form of this equation is motivated by physical observations and derived by an averaging procedure, and we show that it naturally predicts disturbances having the characteristics of slugs and puffs. The model predicts oscillations similar to those which occur in intermittency in pipe flow, but it also predicts that stationary biphasic states can occur in sufficiently short pipes

    Reforming Project Management: The Role of Lean Construction

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    Project management as taught by professional societies and applied in current practice must be reformed because it is inadequate today and its performance will continue to decline as projects become more uncertain, complex and pressed for speed. Project management is failing because of flawed assumptions and idealized theory: it rests on a faulty understanding of the nature or work in projects, and a deficient definition of control. It is argued that a reform of project management will be driven by theories from production management that add the management of workflow and the creation and delivery of value to the current emphasis on activities. Of all the approaches to production management, the theory and principles drawn from Lean Production seem to be best suited for project management. Promising results in this regard have been reached already in one project management area, namely in Lean Construction

    Detecting Unresolved Binaries in TESS Data with Speckle Imaging

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    The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year wide-field survey searching for transiting exoplanets around nearby bright stars that will be ideal for follow-up characterization. To facilitate studies of planet compositions and atmospheric properties, accurate and precise planetary radii need to be derived from the transit light curves. Since 40 - 50% of exoplanet host stars are in multiple star systems, however, the observed transit depth may be diluted by the flux of a companion star, causing the radius of the planet to be underestimated. High angular resolution imaging can detect companion stars that are not resolved in the TESS Input Catalog, or by seeing-limited photometry, to validate exoplanet candidates and derive accurate planetary radii. We examine the population of stellar companions that will be detectable around TESS planet candidate host stars, and those that will remain undetected, by applying the detection limits of speckle imaging to the simulated host star populations of Sullivan et al. (2015) and Barclay et al. (2018). By detecting companions with contrasts of delta m < 7 - 9 and separations of ~0.02 - 1.2'', speckle imaging can detect companion stars as faint as early M stars around A - F stars and stars as faint as mid-M around G - M stars, as well as up to 99% of the expected binary star distribution for systems located within a few hundred parsecs.Comment: Accepted for publication in The Astronomical Journal; 16 pages, 8 figures, 2 table
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