6,283 research outputs found
Engine health monitoring: An advanced system
The advanced propulsion monitoring system is described. The system was developed in order to fulfill a growing need for effective engine health monitoring. This need is generated by military requirements for increased performance and efficiency in more complex propulsion systems, while maintaining or improving the cost to operate. This program represents a vital technological step in the advancement of the state of the art for monitoring systems in terms of reliability, flexibility, accuracy, and provision of user oriented results. It draws heavily on the technology and control theory developed for modern, complex, electronically controlled engines and utilizes engine information which is a by-product of such a system
Magnetic ionization fronts II: Jump conditions for oblique magnetization
We present the jump conditions for ionization fronts with oblique magnetic
fields. The standard nomenclature of R- and D-type fronts can still be applied,
but in the case of oblique magnetization there are fronts of each type about
each of the fast- and slow-mode speeds. As an ionization front slows, it will
drive first a fast- and then a slow-mode shock into the surrounding medium.
Even for rather weak upstream magnetic fields, the effect of magnetization on
ionization front evolution can be important. [Includes numerical MHD models and
an application to observations of S106.]Comment: 9 pages, 10 figures, Latex, to be published in MNRA
Clumpy Ultracompact HII Regions I: Fully Supersonic Wind-blown Models
We propose that a significant fraction of the ultracompact HII regions found
in massive star-forming clouds are the result of the interaction of the wind
and ionizing radiation from a young massive star with the clumpy molecular
cloud gas in its neighbourhood. Distributed mass loading in the flow allows the
compact nebulae to be long-lived. In this paper, we discuss a particularly
simple case, in which the flow in the HII region is everywhere supersonic. The
line profiles predicted for this model are highly characteristic, for the case
of uniform mass loading. We discuss briefly other observational diagnostics of
these models.Comment: To appear in Monthly Notices of the Royal Astronomical Society. 5
pages LaTeX (uses mn.sty and epsf.sty macros) + 4 PS figures. Also available
via http://axp2.ast.man.ac.uk:8000/Preprints.htm
High Resolution CO and H2 Molecular Line Imaging of a Cometary Globule in the Helix Nebula
We report high resolution imaging of a prominent cometary globule in the
Helix nebula in the CO J=1-0 (2.6 mm) and H2 v=1-0 S(1) (2.12 micron) lines.
The observations confirm that globules consist of dense condensations of
molecular gas embedded in the ionized nebula. The head of the globule is seen
as a peak in the CO emission with an extremely narrow line width (0.5 km/s) and
is outlined by a limb-brightened surface of H2 emission facing the central star
and lying within the photo-ionized halo. The emission from both molecular
species extends into the tail region. The presence of this extended molecular
emission provides new constraints on the structure of the tails, and on the
origin and evolution of the globules.Comment: 12 pages, 3 figures. To appear in The Astrophysical Journal Letter
Mathematical modelling of curtain coating
We present a simple mathematical model for the fluid flow in the curtain coating process, exploiting the small aspect ratio, and examine the model in the large-Reynolds-number limit of industrial interest. We show that the fluid is in free fall except for a region close to the substrate, but find that the model can not describe the turning of the curtain onto the substrate. We find that the inclusion of a viscous bending moment close to the substrate allows the curtain to “turn the corner”
VIDEO ANALYSIS OF SHOT DISTRIBUTION AND GOALKEEPER MOVEMENT DURING ROLLER HOCKEY MATCH PLAY
The aim of this investigation was to analyse the position of shots and movement of goalkeepers during roller hockey matches. A video camera recorded the movement of 6 goalkeepers during 6 national roller hockey matches. The position of the goalkeeper and the shots were noted manually from the video recordings. The results showed that, of the 331 shots delivered, the greatest percentage was directed at the bottom corners of the goal. Shots were delivered at a mean interval of 67 s (± 79 s) and of the 34 goals scored the greatest percentage were delivered to the top right corner (38%). Goalkeepers displayed a reasonably high number of movements across the goal; however, the greatest duration was spent covering the central area of the goal (69%). Understanding the match play activity of roller hockey goalkeepers enabled greater task specific training
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