17,793 research outputs found
Ultrasonic scanner for radial and flat panels
An ultrasonic scanning mechanism is described that scans panels of honeycomb construction or with welded seams. It incorporates a device which by simple adjustment is adapted to scan either a flat panel or a radial panel. The supporting structure takes the form of a pair of spaced rails. An immersion tank is positioned between the rails and below their level. A work holder is mounted in the tank and is adapted to hold the flat or radial panel. A traveling bridge is movable along the rails and a carriage is mounted on the bridge
Photon induced secondary electron emission
Numerical models for predicting photon-induced secondary electron emission are presented. The results are compared with experimental measurements made using a Co-60 gamma ray source
Hamiltonian systems with symmetry, coadjoint orbits and plasma physics
The symplectic and Poisson structures on reduced phase spaces are reviewed, including the symplectic structure on coadjoint orbits of a Lie group and the Lie-Poisson structure on the dual of a Lie algebra. These results are
applied to plasma physics. We show in three steps how the Maxwell-Vlasov equations for a collisionless plasma can be written in Hamiltonian form relative to a certain Poisson bracket. First, the Poisson-Vlasov equations are shown
to be in Hamiltonian form relative to the Lie-Poisson bracket on the dual of the (nite dimensional) Lie algebra of innitesimal canonical transformations. Then we write Maxwell's equations in Hamiltonian form using the canonical
symplectic structure on the phase space of the electromagnetic elds, regarded as a gauge theory. In the last step we couple these two systems via the reduction
procedure for interacting systems. We also show that two other standard models in plasma physics, ideal MHD and two-
uid electrodynamics, can be written in Hamiltonian form using similar group theoretic techniques
Chemiluminescent Tags for Tracking Insect Movement in Darkness: Application to Moth Photo-Orientation
The flight tracks of Manduca sexta (Lepidoptera: Sphingidae) flying toward a 5 watt incandescent light bulb were recorded under low light conditions with the aid of a camera-mounted photomultiplier and a glowing marker technique. Small felt pads bearing a chemiluminescent (glowi maerial, Cyalume®, were affixed to the abdomens of free-flying moths. insects orienting to a dim incandescent bulb were easily visible to the naked eye and were clearly captured on videotape. On their initial approach to the light source, M. sexta were found to orient at a mean angle of -0.220 ± 2.70 (mean ± SEM). The speed of the initial approach flight (OA ± 0.03 m/s) was significantly faster than the speed immediately after passing the light (0.29 ± 0.02 m/s; t =6.4, PM. sexta initially fly approximately at a light source and only after passing it, do they engage in circular flight around the source. M. sexta flight to lights does not entirely match any paths predicted by several light orientation mechanisms, including the commonly invoked light compass theory
The inner radio jet region and the complex environment of SS433
We present multi-frequency VLBA+VLA observations of SS433 at 1.6, 5 and 15
GHz. These observations provide the highest angular resolution radio spectral
index maps ever made for this object. Motion of the components of SS433 during
the observation is detected. In addition to the usual VLBI jet structure, we
detect two radio components in the system at an anomalous position angle. These
newly discovered radio emitting regions might be related to a wind-like
equatorial outflow or to an extension of the accretion disk. We show that the
radio core component is bifurcated with a clear gap between the eastern and
western wings of emission. Modelfitting of the precessing jets and the moving
knots of SS433 shows that the kinematic centre -- i.e. the binary -- is in the
gap between the western and eastern radio core components. Spectral properties
and observed core position shifts suggest that we see a combined effect of
synchrotron self-absorption and external free-free absorption in the innermost
AU-scale region of the source. The spatial distribution of the ionized matter
is probably not spherically symmetric around the binary, but could be
disk-like.Comment: Accepted for publication by Astronomy and Astrophysic
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