112,518 research outputs found
LIFE3: A predictive costing tool for digital collections
Predicting the costs of long-term digital preservation is a crucial yet complex task for even the largest repositories and institutions. For smaller projects and individual researchers faced with preservation requirements, the problem is even more overwhelming, as they lack the accumulated experience of the former. Yet being able to estimate future preservation costs is vital to answering a range of important questions for each. The LIFE (Life Cycle Information for E-Literature) project, which has just completed its third phase, helps institutions and researchers address these concerns, reducing the financial and preservation risks, and allowing decision makers to assess a range of options in order to achieve effective preservation while operating within financial restraints. The project is a collaboration between University College London (UCL), The British Library and the Humanities Advanced Technology and Information Institute (HATII) at the University of Glasgow. Funding has been supplied in the UK by the Joint Information Systems Committee (JISC) and the Research Information Network (RIN)
Cusp Summations and Cusp Relations of Simple Quad Lenses
We review five often used quad lens models, each of which has analytical
solutions and can produce four images at most. Each lens model has two
parameters, including one that describes the intensity of non-dimensional mass
density, and the other one that describes the deviation from the circular lens.
In our recent work, we have found that the cusp and the fold summations are not
equal to 0, when a point source infinitely approaches a cusp or a fold from
inner side of the caustic. Based on the magnification invariant theory, which
states that the sum of signed magnifications of the total images of a given
source is a constant, we calculate the cusp summations for the five lens
models. We find that the cusp summations are always larger than 0 for source on
the major cusps, while can be larger or smaller than 0 for source on the minor
cusps. We also find that if these lenses tend to the circular lens, the major
and minor cusp summations will have infinite values, and with positive and
negative signs respectively. The cusp summations do not change significantly if
the sources are slightly deviated from the cusps. In addition, through the
magnification invariants, we also derive the analytical signed cusp relations
on the axes for three lens models. We find that both on the major and the minor
axes the larger the lenses deviated from the circular lens, the larger the
signed cusp relations. The major cusp relations are usually larger than the
absolute minor cusp relations, but for some lens models with very large
deviation from circular lens, the minor cusp relations can be larger than the
major cusp relations.Comment: 8 pages, 4 figures, accepted for publication in MNRA
Lunar magnetization concentrations (MAGCONS) antipodal to young large impact basins
Electron reflection measurements from Apollo 15 and 16 subsatellites show that patches of strong surface magnetic fields ranging in size from less than about 7 km to greater than 500 km are distributed over the surface of the Moon. With the exception of a few regions, no obvious association to surface geology has been found. Researchers examined the antipodes of 23 winged impact basins for which electron reflection measurements are available. It was concluded that the apparent temporal variations for the basin antipodes may reflect real variations in the lunar magnetic field
Evaluation of Formal posterior distributions via Markov chain arguments
We consider evaluation of proper posterior distributions obtained from
improper prior distributions. Our context is estimating a bounded function
of a parameter when the loss is quadratic. If the posterior mean of
is admissible for all bounded , the posterior is strongly
admissible. We give sufficient conditions for strong admissibility. These
conditions involve the recurrence of a Markov chain associated with the
estimation problem. We develop general sufficient conditions for recurrence of
general state space Markov chains that are also of independent interest. Our
main example concerns the -dimensional multivariate normal distribution with
mean vector when the prior distribution has the form on the parameter space . Conditions on for strong
admissibility of the posterior are provided.Comment: Published in at http://dx.doi.org/10.1214/07-AOS542 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Frequency Locking in Spatially Extended Systems
A variant of the complex Ginzburg-Landau equation is used to investigate the
frequency locking phenomena in spatially extended systems. With appropriate
parameter values, a variety of frequency-locked patterns including flats,
fronts, labyrinths and fronts emerge. We show that in spatially
extended systems, frequency locking can be enhanced or suppressed by diffusive
coupling. Novel patterns such as chaotically bursting domains and target
patterns are also observed during the transition to locking
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