2,707 research outputs found

    Can price transparency contribute to more affordable patient access to medicines?

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    Low-Speed Aerodynamic Characteristics of a Fuselage Model with Various Arrangements of Elongated Lift Jets

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    Data were obtained for a round jet located on the center of the bottom of a fuselage and for elongated slots separated spanwise by distances of 0.8 and 1.2 of the fuselage width. The effect of yawing the slots, inclining the jets laterally, and combining slot yaw with jet inclination was determined. Data were obtained in and out of ground effect through a range of effective velocity ratios and through a range of sideslip angles

    Low-speed wind-tunnel investigation of flight spoilers as trailing-vortex-alleviation devices on a medium range wide-body tri-jet airplane model

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    An investigation was made in the V/STOL tunnel to determine, by the trailing wing sensor technique, the effectiveness of various segments of the existing flight spoilers on a medium range wide body tri-jet transport airplane model when they were deflected as trailing vortex alleviation devices. The four combinations of flight spoiler segments investigated were effective in reducing the induced rolling moment on the trailing wing model by as much as 15 to 60 percent at distances behind the transport model of from 3.9 to 19.6 transport wing spans, 19.6 spans being the downstream limit of distances used. Essentially all of the reduction in induced rolling moment on the trailing wing model was realized at a spoiler deflection of about 45 deg

    Comparison of aerodynamic theory and experiment for jet-flap wings

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    Aerodynamic theory predictions made for a jet flapped wing were compared with experimental data obtained in a fairly extensive series of tests in the Langley V/STOL tunnel. The tests were made on a straight, rectangular wing and investigated two types of jet flap concepts: a pure jet flap with high jet deflection and a wing with blowing at the knee of a plain trailing edge flap. The tests investigated full and partial span blowing for wing aspect ratios of 8.0 and 5.5 and momentum coefficients from 0 to about 4. The total lift, drag, and pitching moment coefficients predicted by the theory were in excellent agreement with experimental values for the pure jet flap, even with the high jet deflection. The pressure coefficients on the wing, and hence the circulation lift coefficients, were underpredicted, however, because of the linearizing assumptions of the planar theory. The lift, drag, and pitching moment coefficients, as well as pressure coefficients, were underpredicted for the wing with blowing over the flap because of the failure of the theory to account for the interaction effect of the high velocity jet passing over the flap

    Controlling the dynamics of an open many-body quantum system with localized dissipation

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    We experimentally investigate the action of a localized dissipative potential on a macroscopic matter wave, which we implement by shining an electron beam on an atomic Bose-Einstein condensate (BEC). We measure the losses induced by the dissipative potential as a function of the dissipation strength observing a paradoxical behavior when the strength of the dissipation exceeds a critical limit: for an increase of the dissipation rate the number of atoms lost from the BEC becomes lower. We repeat the experiment for different parameters of the electron beam and we compare our results with a simple theoretical model, finding excellent agreement. By monitoring the dynamics induced by the dissipative defect we identify the mechanisms which are responsible for the observed paradoxical behavior. We finally demonstrate the link between our dissipative dynamics and the measurement of the density distribution of the BEC allowing for a generalized definition of the Zeno effect. Due to the high degree of control on every parameter, our system is a promising candidate for the engineering of fully governable open quantum systems

    Path sampling for lifetimes of metastable magnetic skyrmions and direct comparison with Kramers' method

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    We perform a direct comparison between Kramers' method in many dimensions -- i.e., Langer's theory -- adapted to magnetic spin systems, and a path sampling method in the form of forward flux sampling, as a means to compute collapse rates of metastable magnetic skyrmions. We show that a good agreement is obtained between the two methods. We report variations of the attempt frequency associated with skyrmion collapse by three to four orders of magnitude when varying the applied magnetic field by 5%\% of the exchange strength, which confirms the existence of a strong entropic contribution to the lifetime of skyrmions. This demonstrates that in complex systems, the knowledge of the rate prefactor, in addition to the internal energy barrier, is essential in order to properly estimate a lifetime.Comment: 5 pages, 5 figures (main text), 8 pages including supplemental materia

    Ground effects on single-jet and multiple-jet VTOL models at transition speeds over stationary and moving ground planes

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    Ground effects on single and multiple jet VTOL WING fuselage models at transition speeds over stationary and moving ground plane

    Wind tunnel investigation of internally blown jet-flap STOL airplane model

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    The low speed longitudinal characteristics of the jet flap STOL model were determined. The 17 percent thick supercritical swept wing had leading edge slats and a full span 0.30 chord plain flap with flaperons divided into six equal spanwise segments. The angle of attack range was -4 deg to 24 deg, and the blowing momentum range was from 0 to 2.3. Flap deflections were from 0 deg to 70 deg. Most flap deflections were full span although there were some tests of partial span deflections and partial span blowing
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