70,198 research outputs found
Measurement of the derivative 'ZW' for an oscillating aerofoil
This report presents the results of experimental
measurements of the damping derivative coefficient zw for
constant chord rigid wings of various aspect ratios having
sweepback angles of zero and 450.
The results for the rectangular wings Flow substantial
agreement with the unsteady aerofoil theory developed
by TI.P. Jones $2) The dependence of Zvi upon frequency parameter
is as given by theory and is much less than for two dimensional
flow, but the numerical results are approximately
10 per cent below the theoretical. This is attributed to the
large trailing edge angle 22° of the N.A.C.A. 0020 section
used for the model aerofoils.
The effect of sweepback is to decrease the numerical
value of z , but this effect is much less pronounced, for low
than for high aspect ratios. For aspect ratios 5 and 3
the numerical value is greater than would be given by a factor
of proportionality equal to the cosine of the angle of
sweepback.
The measurements were corrected for tunnel interference
by a method based on the theoretical work of 7.P.Jones.(1
Spine-sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87
Simple one-zone homogeneous synchrotron self-Compton models have severe
difficulties in explaining the TeV emission observed in the radiogalaxy M87.
Also the site of the TeV emission region is uncertain: it could be the
unresolved jet close to the nucleus, analogously to what proposed for blazars,
or an active knot, called HST-1, tens of parsec away. We explore the
possibility that the TeV emission of M87 is produced in the misaligned subpc
scale jet. We base our modelling on a structured jet, with a fast spine
surrounded by a slower layer. In this context the main site responsible for the
emission of the TeV radiation is the layer, while the (debeamed) spine accounts
for the emission from the radio to the GeV band: therefore we expect a more
complex correlation with the TeV component than that expected in one-zone
scenarios, in which both components are produced by the same region. Observed
from small angles, the spine would dominate the emission, with an overall
Spectral Energy Distribution close to those of BL Lac objects with a
synchrotron peak located at low energy (LBLs).Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter
Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
The structures of globular clusters (GCs) reflect their dynamical states and
past histories. High-resolution imaging allows the exploration of morphologies
of clusters in other galaxies. Surface brightness profiles from new Hubble
Space Telescope observations of 34 globular clusters in M31 are presented,
together with fits of several different structural models to each cluster. M31
clusters appear to be adequately fit by standard King models, and do not
obviously require alternate descriptions with relatively stronger halos, such
as are needed to fit many GCs in other nearby galaxies. The derived structural
parameters are combined with corrected versions of those measured in an earlier
survey to construct a comprehensive catalog of structural and dynamical
parameters for M31 GCs with a sample size similar to that for the Milky Way.
Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and
NGC 5128 define a very tight fundamental plane with identical slopes. The
combined evidence for these widely different galaxies strongly reinforces the
view that old globular clusters have near-universal structural properties
regardless of host environment.Comment: AJ in press; 59 pages including 16 figure
Positive psychology and romantic scientism: Reply to comments on Brown, Sokal, & Friedman (2013)
This is a response to five comments [American Psychologist 69, 626-629 and
632-635 (2014)] on our article arXiv:1307.7006.Comment: PDF, 9 page
The persistence of wishful thinking: Response to "Updated thinking on positivity ratios"
This is a response to Barbara Fredrickson's comment [American Psychologist
68, 814-822 (2013)] on our article arXiv:1307.7006.
We analyze critically the renewed claims made by Fredrickson (2013)
concerning positivity ratios and "flourishing", and attempt to disentangle some
conceptual confusions; we also address the alleged empirical evidence for
nonlinear effects. We conclude that there is no evidence whatsoever for the
existence of any "tipping points", and only weak evidence for the existence of
any nonlinearity of any kind. Our original concern, that the application of
advanced mathematical techniques in psychology and related disciplines may not
always be appropriate, remains undiminished.Comment: LaTeX2e, 10 pages including 6 Postscript figure
Design and development of a self-healing fuse
Mercury-filled self-healing fuses for protecting solid state circuits from faults - design and developmen
Phase 2 and 3 wind tunnel tests of the J-97 powered, external augmentor V/STOL model
Static and forward speed tests were made in a 40 multiplied by 80 foot wind tunnel of a large-scale, ejector-powered V/STOL aircraft model. Modifications were made to the model following earlier tests primarily to improve longitudinal acceleration capability during transition from hovering to wingborne flight. A rearward deflection of the fuselage augmentor thrust vector was shown to be beneficial in this regard. Other augmentor modifications were tested, notably the removal of both endplates, which improved acceleration performance at the higher transition speeds. The model tests again demonstrated minimal interference of the fuselage augmentor on aerodynamic lift. A flapped canard surface also showed negligible influence on the performance of the wing and of the fuselage augmentor
Self-healing fuse
Fast-acting current limiting device provides current overload protection for vulnerable circuit elements and then re-establishes conduction path within milliseconds. Fuse can also perform as fast-acting switch to clear transient circuit overloads. Fuse takes advantage of large increase in electrical resistivity that occurs when liquid metal vaporizes
- …