6,387 research outputs found

    An experimental study of plane mixing layer development

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    Mean flow and turbulence was measured in the near field of two plane mixing layers in air with a maximum velocity of 21 m/sec. The experimental rig enabled mixing layers of velocity ratios 0 and 0.46 to be generated simultaneously. Gases with both tripped and untripped initial boundary layers were studied. It was found that the two stream layer developed to the self preserving state in a distance much shorter than did the single stream layer which followed accepted criteria for the development distance. The asymptotic levels of the turbulence quantities in the two stream layer and the development of the single stream layer showed agreement with existing data. It is suggested that the two stream mixing layer should provide a better test case for the development of turbulence models and calculation methods than the single stream mixing layer

    The Price of Updating the Control Plane in Information-Centric Networks

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    We are studying some fundamental properties of the interface between control and data planes in Information-Centric Networks. We try to evaluate the traffic between these two planes based on allowing a minimum level of acceptable distortion in the network state representation in the control plane. We apply our framework to content distribution, and see how we can compute the overhead of maintaining the location of content in the control plane. This is of importance to evaluate content-oriented network architectures: we identify scenarios where the cost of updating the control plane for content routing overwhelms the benefit of fetching a nearby copy. We also show how to minimize the cost of this overhead when associating costs to peering traffic and to internal traffic for operator-driven CDNs.Comment: 10 pages, 12 figure

    Double-branched vortex generator

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    In order to assess the suitability of using a double branched vortex generator in parametric studies involving vortex interactions, an experimental study of the main vortex and secondary flows produced by a double branched vortex generator was conducted in a 20-by-40 cm indraft wind tunnel. Measurements of the cross flow velocities were made with a five hole pressure probe from which vorticity contours and vortex parameters were derived. The results showed that the optimum configuration consisted of chord extensions with the absence of a centerbody

    Development of subminiature multi-sensor hot-wire probes

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    Limitations on the spatial resolution of multisensor hot wire probes have precluded accurate measurements of Reynolds stresses very near solid surfaces in wind tunnels and in many practical aerodynamic flows. The fabrication, calibration and qualification testing of very small single horizontal and X-array hot-wire probes which are intended to be used near solid boundaries in turbulent flows where length scales are particularly small, is described. Details of the sensor fabrication procedure are reported, along with information needed to successfully operate the probes. As compared with conventional probes, manufacture of the subminiature probes is more complex, requiring special equipment and careful handling. The subminiature probes tested were more fragile and shorter lived than conventional probes; they obeyed the same calibration laws but with slightly larger experimental uncertainty. In spite of these disadvantages, measurements of mean statistical quantities and spectra demonstrate the ability of the subminiature sensors to provide the measurements in the near wall region of turbulent boundary layers that are more accurate than conventional sized probes

    Thought Experiments, Epistemology & our Cognitive (In)Capacities

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    Does epistemology collapse for lack of resources other than logic, conceptual analysis and descriptions of one’s own apparent experiences, thoughts and beliefs? No, but understanding how and why not requires, Kant noted, a ‘changed method of thinking’ (veränderte Methode der Denkungsart; KdrV Bxvii, 704). Some of these methodological changes are summarised in §2 in order to identify a philosophical role for thought experiments to help identify logically contingent, though cognitively fundamental capacities and circumstances necessary to human thought, experience and knowledge. As Kant also noted, experiments are only informative in response to posing the right question, indeed: the right kind of question (KdrV Bxii–xiv). Accordingly, preparations for these epistemological thought experiments (§2) fill half of this chapter. The second half (§§3–5), examines three such thought experiments, variously developed by Kant, Hegel, C. I. Lewis, Austin, Wittgenstein and F. L. Will

    A Comparison of Attitude Change in Senior Citizen and College Age Subjects

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    The present study was designed to examine the validity of generally held assumptions of decreased attitudinal flexibility in the aged. A preliminary study preceded the formal study and identified a target attitude, sources of varying credibility, and evaluated self-esteem as a possible confounding variable. Subsequently 40 college age and 40 senior citizen subjects\u27 attitude toward the Equal Rights Amendment were measured by a paper and pencil survey. Two weeks later an anti- E.R.A. attitude change message, attributed to sources of varying age and credibility, was presented and its impact measured by a posttest survey. Follow-up measures were taken three weeks later. An analysis of covariance yielded a significant subject age effect at the posttest with greater attitude change exhibited by the senior citizens. Neither source age nor source credibility main effects reached significance and there were no significant interactions. On the follow-up measure there were no significant main effects or interactions, though subject age approached significance. The results were interpreted as being contrary to assumptions of increased rigidity in the elderly and not supportive of the decrement model of aging. Methodological difficulties were discussed with respect to the results found and further research was recommended
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