8,592 research outputs found

    Investigation of the flaw growth characteristics of 6Al-4V titanium used in the Apollo spacecraft pressure vessels

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    Failure analysis of flaw growth characteristics of 6Al-4V titanium forgings used in Apollo spacecraft propellant tank

    Maximum Angular Separation Epochs for Exoplanet Imaging Observations

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    Direct imaging of exoplanets presents both significant challenges and significant gains. The advantages primarily lie in receiving emitted and, with future instruments, reflected photons at phase angles not accessible by other techniques, enabling the potential for atmospheric studies and the detection of rotation and surface features. The challenges are numerous and include coronagraph development and achieving the necessary contrast ratio. Here, we address the specific challenge of determining epochs of maximum angular separation for the star and planet. We compute orbital ephemerides for known transiting and radial velocity planets, taking Keplerian orbital elements into account. We provide analytical expressions for angular star--planet separation as a function of the true anomaly, including the locations of minimum and maximum. These expressions are used to calculate uncertainties for maximum angular separation as a function of time for the known exoplanets, and we provide strategies for improving ephemerides with application to proposed and planned imaging missions.Comment: 7 pages, 3 figures, 1 table, accepted for publication in the Astronomical Journa

    Units of Evidence for Analyzing Subdisciplinary Difference in Data Practice Studies

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    Digital libraries (DLs) are adapting to accommodate research data and related services. The complexities of this new content spans the elements of DL development, and there are questions concerning data selection, service development, and how best to align these with local, institutional initiatives for cyberinfrastructure, data-intensive research, and data stewardship. Small science disciplines are of particular relevance due to the prevalence of this mode of research in the academy, and the anticipated magnitude of data production. To support data acquisition into DLs – and subsequent data reuse – there is a need for new knowledge on the range and complexities inherent in practice-data-curation arrangements for small science research. We present a flexible methodological approach crafted to generate data units to analyze these relationships and facilitate crossdisciplinary comparisons.Library Services (LG-06-07-0032-07) and National Science Foundation (OCI-0830976).is peer reviewe

    Investigation of crack growth threshold of Inconel 718 exposed to high pressure oxygen Final report 24 Apr. - 25 May 1970

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    Crack growth threshold investigation of Inconel 718 exposed to high pressure oxyge
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