13,605 research outputs found

    Non-extremal instantons and wormholes in string theory

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    We construct the most general non-extremal spherically symmetric instanton solution of a gravity-dilaton-axion system with SL(2,R)SL(2,R) symmetry, for arbitrary euclidean spacetime dimension D≥3D\geq 3. A subclass of these solutions describe completely regular wormhole geometries, whose size is determined by an invariant combination of the SL(2,R)SL(2,R) charges. Our results can be applied to four-dimensional effective actions of type II strings compactified on a Calabi-Yau manifold, and in particular to the universal hypermultiplet coupled to gravity. We show that these models contain regular wormhole solutions, supported by regular dilaton and RR scalar fields of the universal hypermultiplet.Comment: 10 pages, to appear in the proceedings of the RTN2004 workshop, Kolymbari, Crete, 5-10 September, Greec

    The effect of wavy leading edges on aerofoil-gust interaction noise

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    High-order accurate numerical simulations are performed to investigate the effects of wavy leading edges (WLEs) on aerofoil–gust interaction (AGI) noise. The present study is based on periodic velocity disturbances predominantly in streamwise and vertical directions that are mainly responsible for the surface pressure fluctuation of an aerofoil. In general, the present results show that WLEs lead to reduced AGI noise. It is found that the ratio of the wavy leading-edge peak-to-peak amplitude (LEA) to the longitudinal wavelength of the incident gust (?g) is the most important factor for the reduction of AGI noise. It is observed that there exists a tendency that the reduction of AGI noise increases with LEA/?g and the noise reduction is significant for LEA/?g?0.3. The present results also suggest that any two different cases with the same LEA/?g lead to a strong similarity in their profiles of noise reduction relative to the straight leading-edge case. The wavelength of wavy leading edges (LEW), however, shows minor influence on the reduction of AGI noise under the present gust profiles used. Nevertheless, the present results show that a meaningful improvement in noise reduction may be achieved when 1.0?LEW/?g?1.5. In addition, it is found that the beneficial effects of WLEs are maintained for various flow incidence angles and aerofoil thicknesses. Also, the WLEs remain effective for gust profiles containing multiple frequency components. It is discovered in this paper that WLEs result in incoherent response time to the incident gust across the span, which results in a decreased level of surface pressure fluctuations, hence a reduced level of AGI noise

    The Brockport Staffing Model

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    Open Educational Resources: CELT Presentation

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    Presentation given at CELT to introduce faculty to the SUNY OER initiative, with details on what OER is, and how the incentive might work at Brockport

    Getting Started in Library Publishing

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    Lightning round presentation given at the 2016 NYLA Scholarly Communication Unconference at Saratoga Springs, NY on November 2, 2016

    Faculty/Staff Technology Support Initiative: Next Engine 3D Scanner

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    The Next Engine 3D Scanner would enhance and promote the use of the Makerbot Replicator 3D Printer that has recently been purchased for use by students and faculty who wish to explore this innovative technology and incorporate it into the curriculum. The scanner increases the 3D printer’s usefulness by allowing existing objects to be scanned and printed, rather than just designed from scratch. The MultiDrive Scanning Platform further automates and increases ease of use of the process. The upgraded software increases the speed and ease of the scanning process. With creator’s consent, object plans can then be added to the institutional repository, Digital Commons@Brockport

    The Library as YOUR Research Partner

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    Presented at the 2016 Grant Writing Workshop, with the goal of helping attendees realize that the library is their research partner. From finding and obtaining resources, and individual research consultations, to getting an ORCiD and setting up a research profile, Drake Library staff stand ready to help
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