4,184 research outputs found

    Space-time correlations in turbulent flow: A review

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    This paper reviews some of the principal uses, over almost seven decades, of correlations, in both Eulerian and Lagrangian frames of reference, of properties of turbulent flows at variable spatial locations and variable time instants. Commonly called space--time correlations, they have been fundamental to theories and models of turbulence as well as for the analyses of experimental and direct numerical simulation turbulence data.Comment: 16 pages, 7 figure

    Guidelines for the Provision of Garbage Reception Facilities at Ports Under MARPOL Annex V

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    This report offers guidelines for the provision of adequate port reception facilities for vessel-generated garbage under the requirements of Annex V of the International Convention for the Prevention of Pollution From Ships, 1973 (MARPOL 73/78), Regulations for the Prevention of Pollution by Garbage from Ships. MARPOL Annex V prohibits at-sea disposal of plastic materials from vessels, and specifies the distance from shore at which other materials may be dumped. Annex V also requires the provision of port reception facilities for garbage, but it does not specify these facilities or how they are to be provided. Since the at-sea dumping restrictions apply to all vessels, the reception facility requirement applies to all ports, terminals, and marinas that serve vessels. These guidelines were prepared to assist port owners and operators in meeting their obligation to provide adequate reception facilities for garbage. The report synthesizes available information and draws upon experience from the first years ofimplementation of MARPOL Annex V. (PDF file contains 55 pages.

    Commercial Transactions

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    Inventory of Lake Studies in Maine

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    Inventory of Lake Studies in Maine By Charles F. Wallace, Jr. and James M. Strunk State Planning Office, Water Resources Planning Division, July 1973. Printed under Appropriation Number 4248.5 and financially assisted by planning grants from the United States Water Resources Council Title III funds. Contents: Introduction / Investigating Agencies / Federal Agencies / State Agencies / Regional Planning Commissions and Economic Development Districts / Maine Colleges and Universities / Private / Other Private / Other / Appendiceshttps://digitalcommons.usm.maine.edu/me_collection/1134/thumbnail.jp

    The Impact Of Management Security Control Consciousness On Security Control Activities: Implications For Compliance With The Sarbanes-Oxley Act

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    Using information system audit documentation from 60 clients of a Big 4 firm, we extend Kizirian (2004) by examining whether management security control consciousness (i.e., the “tone at the top”) influences (1) security control activities performed by the client, and (2) the auditor’s firm-wide (i.e., global) assessment of security control.  Findings suggest that management control consciousness results in the employment of security controls.  The auditor’s assessment of the strength of management control consciousness can also affect the auditor’s assessment of the client’s global security control.  While our data pre-dates the Sarbanes-Oxley Act, our findings speak to the importance of assessing an organization's tone at the top, and thus, have implications for auditors working to certify a client’s compliance with the Sarbanes-Oxley Act

    Investigation of Cracks Found in Helicopter Longerons

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    Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces

    A fast scintillator Compton telescope for medium-energy gamma-ray astronomy

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    The field of medium-energy gamma-ray astronomy urgently needs a new mission to build on the success of the COMPTEL instrument on the Compton Gamma Ray Observatory. This mission must achieve sensitivity significantly greater than that of COMPTEL in order to advance the science of relativistic particle accelerators, nuclear astrophysics, and diffuse backgrounds, and bridge the gap between current and future hard X-ray missions and the high-energy Fermi mission. Such an increase in sensitivity can only come about via a dramatic decrease in the instrumental background. We are currently developing a concept for a low-background Compton telescope that employs modern scintillator technology to achieve this increase in sensitivity. Specifically, by employing LaBr3 scintillators for the calorimeter, one can take advantage of the unique speed and resolving power of this material to improve the instrument sensitivity while simultaneously enhancing its spectroscopic and imaging performance. Also, using deuterated organic scintillator in the scattering detector will reduce internal background from neutron capture. We present calibration results from a laboratory prototype of such an instrument, including time-of-flight, energy, and angular resolution, and compare them to simulation results using a detailed Monte Carlo model. We also describe the balloon payload we have built for a test flight of the instrument in the fall of 2010

    A new low-background Compton telescope using LaBr3 scintillator

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    Gamma-ray astronomy in the MeV range suffers from weak fluxes from sources and high background in the nuclear energy range. The background comes primarily from neutron-induced gamma rays, with the neutrons being produced by cosmic-ray interactions in the Earth\u27s atmosphere, the spacecraft, and the instrument. Compton telescope designs often suppress this background by requiring coincidences in multiple detectors and a narrow time-of-flight (ToF) acceptance window. The COMPTEL experience on the Compton Gamma Ray Observatory shows that a 1.9-ns ToF resolution is insufficiently narrow to achieve the required low background count rate. Furthermore, neutron interactions in the detectors themselves generate an irreducible background. By employing LaBr3 scintillators for the calorimeter, one can take advantage of the unique speed and resolving power of the material to improve the instrument sensitivity and simultaneously enhance its spectroscopic performance and thus its imaging performance. We present a concept for a balloon- or space-borne Compton telescope that employs deuterated liquid in the scattering detector and LaBr3 as a calorimeter and estimate the improvement in sensitivity over past realizations of Compton telescopes. We show initial laboratory test results from a small prototype, including energy and timing resolution. Finally, we describe our plan to fly this prototype on a test balloon flight to directly validate our background predictions and guide the development of a full-scale instrument
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