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Circular Disc (circular + disc)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Analysis on a novel ultra-wide bandwidth antenna of double-printed circular disc

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007
Yi-Min Lu
Abstract A novel ultra-wide bandwidth antenna of double-printed circular disc is presented in this article. Some reasonable theoretical analyses are proposed. Printed on the dielectric substrate and fed by a microstrip line, the antenna has been demonstrated to provide an UWB with return loss less than ,10 dB from 3.1 to 10.6 GHz and the satisfactory radiation properties. In addition, an even better impedance matching can be got by improved the feed point, which is quite valuable for broadband antennas design. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 311,313, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22115 [source]

Stellar dynamical evidence against a cold disc origin for stars in the Galactic Centre

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2008
Jorge Cuadra
ABSTRACT Observations of massive stars within the central parsec of the Galaxy show that, while most stars orbit within a well-defined disc, a significant fraction have large eccentricities and/or inclinations with respect to the disc plane. Here, we investigate whether this dynamically hot component could have arisen via scattering from an initially cold disc , the expected initial condition if the stars formed from the fragmentation of an accretion disc. Using N -body methods, we evolve a variety of flat, cold, stellar systems, and study the effects of initial disc eccentricity, primordial binaries, very massive stars and intermediate mass black holes. We find, consistent with previous results, that a circular disc does not become eccentric enough unless there is a significant population of undetected 100,1000 M, objects. However, since fragmentation of an eccentric disc can readily yield eccentric stellar orbits, the strongest constraints come from inclinations. We show that none of our initial conditions yields the observed large inclinations, regardless of the initial disc eccentricity or the presence of massive objects. These results imply that the orbits of the young massive stars in the Galactic Centre are largely primordial, and that the stars are unlikely to have formed as a dynamically cold disc. [source]

A general model for porous medium flow in squeezing film situations

LUBRICATION SCIENCE, Issue 2 2010
Mohamed Nabhani
Abstract The present paper deals with a numerical investigation of the hydrodynamic lubrication of a porous squeeze film between two circular discs. To this purpose, the thin film (reduced) Navier Stokes equations and a generalised porous medium model are solved. The numerical results show that the effect of the porous disc is to reduce the lubricating properties of the fluid film. This effect is increased during the squeezing action. In addition, it is shown that the film pressure, the load-carrying capacity and the velocity field based only on the Darcy model are predicted higher than those obtained from the generalised porous medium model. Copyright © 2009 John Wiley & Sons, Ltd. [source]