476 research outputs found
Detection of spatial pattern through independence of thinned processes
Let N, N' and N'' be point processes such that N' is obtained from N by
homogeneous independent thinning and N''= N- N'. We give a new elementary proof
that N' and N'' are independent if and only if N is a Poisson point process. We
present some applications of this result to test if a homogeneous point process
is a Poisson point process.Comment: 11 pages, one figur
Provisioning Spot Market Cloud Resources to Create Cost-effective Virtual Clusters
Infrastructure-as-a-Service providers are offering their unused resources in
the form of variable-priced virtual machines (VMs), known as "spot instances",
at prices significantly lower than their standard fixed-priced resources. To
lease spot instances, users specify a maximum price they are willing to pay per
hour and VMs will run only when the current price is lower than the user's bid.
This paper proposes a resource allocation policy that addresses the problem of
running deadline-constrained compute-intensive jobs on a pool of composed
solely of spot instances, while exploiting variations in price and performance
to run applications in a fast and economical way. Our policy relies on job
runtime estimations to decide what are the best types of VMs to run each job
and when jobs should run. Several estimation methods are evaluated and
compared, using trace-based simulations, which take real price variation traces
obtained from Amazon Web Services as input, as well as an application trace
from the Parallel Workload Archive. Results demonstrate the effectiveness of
running computational jobs on spot instances, at a fraction (up to 60% lower)
of the price that would normally cost on fixed priced resources.Comment: 14 pages, 4 figures, 11th International Conference on Algorithms and
Architectures for Parallel Processing (ICA3PP-11); Lecture Notes in Computer
Science, Vol. 7016, 201
Neutron Transfer reactions induced by 8Li on 9Be
Angular distributions for the elastic scattering of 8Li on 9Be and the
neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been
measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for
8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between
the experimental differential cross section and finite-range DWBA calculations
with the code FRESCO. The spectroscopic factors obtained are compared to shell
model calculations and to other experimental values from (d,p) reactions. Using
the present values for the spectroscopic factor, cross sections for the direct
neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the
framework of a potential model.Comment: 24 pages, 8 Figures, submitted as regular article to PR
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