3,246 research outputs found
Recommended from our members
Reliability and fault tolerance modelling of multiprocessor systems
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Reliability evaluation by analytic modelling constitute an important issue of designing a reliable multiprocessor system. In this thesis, a model for reliability and fault tolerance analysis of the interconnection network is presented, based on graph theory. Reliability and fault tolerance are considered as deterministic and probabilistic measures of connectivity.
Exact techniques for reliability evaluation fail for large multiprocessor systems because of the enormous computational resources required. Therefore, approximation techniques have to be used. Three approaches are proposed, the first by simplifying the symbolic expression of reliability; the
other two by applying a hierarchical decomposition to the system. All these
methods give results close to those obtained by exact techniques.Consejo Nacional de Ciencia y Tecnologia" (National Council for Science and Technology of Mexico) and "Instituto de Investigaciones Electricas" (Institute for Electrical Research
The dragonfly nearby galaxies survey. Iv. A giant stellar disk in ngc 2841
Neutral gas is commonly believed to dominate over stars in the outskirts of
galaxies, and investigations of the disk-halo interface are generally
considered to be in the domain of radio astronomy. This may simply be a
consequence of the fact that deep HI observations typically probe to a lower
mass surface density than visible wavelength data. This paper presents low
surface brightness optimized visible wavelength observations of the extreme
outskirts of the nearby spiral galaxy NGC 2841. We report the discovery of an
enormous low-surface brightness stellar disk in this object. When azimuthally
averaged, the stellar disk can be traced out to a radius of 70 kpc (5
or 23 inner disk scale lengths). The structure in the stellar disk
traces the morphology of HI emission and extended UV emission. Contrary to
expectations, the stellar mass surface density does not fall below that of the
gas mass surface density at any radius. In fact, at all radii greater than
20 kpc, the ratio of the stellar to gas mass surface density is a
constant 3:1. Beyond 30 kpc, the low surface brightness stellar disk
begins to warp, which may be an indication of a physical connection between the
outskirts of the galaxy and infall from the circumgalactic medium. A
combination of stellar migration, accretion and in-situ star formation might be
responsible for building up the outer stellar disk, but whatever mechanisms
formed the outer disk must also explain the constant ratio between stellar and
gas mass in the outskirts of this galaxy.Comment: 11 pages, 5 figures, accepted for publication in Ap
- …