1,568 research outputs found
Partitioning workflow applications over federated clouds to meet non-functional requirements
PhD ThesisWith cloud computing, users can acquire computer resources when they need them
on a pay-as-you-go business model. Because of this, many applications are now being
deployed in the cloud, and there are many di erent cloud providers worldwide. Importantly,
all these various infrastructure providers o er services with di erent levels
of quality. For example, cloud data centres are governed by the privacy and security
policies of the country where the centre is located, while many organisations have
created their own internal \private cloud" to meet security needs.
With all this varieties and uncertainties, application developers who decide to host their
system in the cloud face the issue of which cloud to choose to get the best operational
conditions in terms of price, reliability and security. And the decision becomes even
more complicated if their application consists of a number of distributed components,
each with slightly di erent requirements.
Rather than trying to identify the single best cloud for an application, this thesis
considers an alternative approach, that is, combining di erent clouds to meet users'
non-functional requirements. Cloud federation o ers the ability to distribute a single
application across two or more clouds, so that the application can bene t from the
advantages of each one of them. The key challenge for this approach is how to nd the
distribution (or deployment) of application components, which can yield the greatest
bene ts. In this thesis, we tackle this problem and propose a set of algorithms, and a
framework, to partition a work
ow-based application over federated clouds in order to
exploit the strengths of each cloud. The speci c goal is to split a distributed application
structured as a work
ow such that the security and reliability requirements of each
component are met, whilst the overall cost of execution is minimised.
To achieve this, we propose and evaluate a cloud broker for partitioning a work
ow
application over federated clouds. The broker integrates with the e-Science Central
cloud platform to automatically deploy a work
ow over public and private clouds.
We developed a deployment planning algorithm to partition a large work
ow appli-
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cation across federated clouds so as to meet security requirements and minimise the
monetary cost.
A more generic framework is then proposed to model, quantify and guide the partitioning
and deployment of work
ows over federated clouds. This framework considers
the situation where changes in cloud availability (including cloud failure) arise during
work
ow execution
scalar glueball in finite-width Gaussian sum rules
Based on a semiclassical expansion for quantum chromodynamics in the
instanton liquid background, the correlation function of the scalar
glueball current is given, and the properties of the scalar glueball
are studied in the framework of Gaussian sum rules. Besides the pure classical
and quantum contributions, the contributions arising from the interactions
between the classical instanton fields and quantum gluons are come into play.
Instead of the usual zero-width approximation for the resonance, the
Breit-Wigner form for the spectral function of the finite-width resonance is
adopted. The family of the Gaussian sum rules for the scalar glueball in
quantum chromodynamics with and without light quarks is studied. A consistency
between the subtracted and unsubtracted sum rules is very well justified, and
the values of the decay width and the coupling to the corresponding current for
the resonance, in which the scalar glueball fraction is dominant, are
obtained.Comment: 18pages, 9figure
Vortex images on Ba{1-x}KxFe2As2 observed directly by the magnetic force microscopy
The vortex states on optimally doped Ba0.6K0.4Fe2As2 and underdoped
Ba0.77K0.23Fe2As2 single crystals are imaged by magnetic force microscopy at
various magnetic fields below 100 Oe. Local triangular vortex clusters are
observed in optimally doped samples. The vortices are more ordered than those
in Ba(Fe{1-x}Co{x})2As2, and the calculated pinning force per unit length is
about 1 order of magnitude weaker than that in optimally Co-doped 122 at the
same magnetic field, indicating that the Co doping at the Fe sites induces
stronger pinning. The proportion of six-neighbored vortices to the total amount
increases quickly with increasing magnetic field, and the estimated value
reaches 100% at several tesla. Vortex chains are also found in some local
regions, which enhance the pinning force as well as the critical current
density. Lines of vortex chains are observed in underdoped samples, and they
may have originated from the strong pinning near the twin boundaries arising
from the structural transition.Comment: 7 pages, 8 figure
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