1,151 research outputs found
Functional adaptivity for digital library services in e-infrastructures: the gCube approach
We consider the problem of e-Infrastructures that wish to reconcile the generality of their services with the bespoke requirements of diverse user communities. We motivate the requirement of functional adaptivity in the context of gCube, a service-based system that integrates Grid and Digital Library technologies to deploy, operate, and monitor Virtual Research Environments defined over infrastructural resources. We argue that adaptivity requires mapping service interfaces onto multiple implementations, truly alternative interpretations of the same functionality. We then analyse two design solutions in which the alternative implementations are, respectively, full-fledged services and local components of a single service. We associate the latter with lower development costs and increased binding flexibility, and outline a strategy to deploy them dynamically as the payload of service plugins. The result is an infrastructure in which services exhibit multiple behaviours, know how to select the most appropriate behaviour, and can seamlessly learn new behaviours
Remote data acquisition for condition monitoring of wind turbines
While the number of offshore wind turbines is growing and turbines getting bigger and more expensive, the need for good condition monitoring systems is rising. From the research it is clear that failures of the gearbox, and in particular the gearwheels and bearings of the gearbox, have been responsible for the most downtime of a wind turbine. Gearwheels and bearings are being simulated in a multi-sensor environment to observe the wear on the surface
Weyl node with random vector potential
We study Weyl semimetals in the presence of generic disorder, consisting of a
random vector potential as well as a random scalar potential. We derive
renormalization group flow equations to second order in the disorder strength.
These flow equations predict a disorder-induced phase transition between a
pseudo-ballistic weak-disorder phase and a diffusive strong-disorder phase for
sufficiently strong random scalar potential or for a pure three-component
random vector potential. We verify these predictions using a numerical study of
the density of states near the Weyl point and of quantum transport properties
at the Weyl point. In contrast, for a pure single-component random vector
potential the diffusive strong-disorder phase is absent.Comment: published version with minor change
Equivariant semidefinite lifts and sum-of-squares hierarchies
A central question in optimization is to maximize (or minimize) a linear
function over a given polytope P. To solve such a problem in practice one needs
a concise description of the polytope P. In this paper we are interested in
representations of P using the positive semidefinite cone: a positive
semidefinite lift (psd lift) of a polytope P is a representation of P as the
projection of an affine slice of the positive semidefinite cone
. Such a representation allows linear optimization problems
over P to be written as semidefinite programs of size d. Such representations
can be beneficial in practice when d is much smaller than the number of facets
of the polytope P. In this paper we are concerned with so-called equivariant
psd lifts (also known as symmetric psd lifts) which respect the symmetries of
the polytope P. We present a representation-theoretic framework to study
equivariant psd lifts of a certain class of symmetric polytopes known as
orbitopes. Our main result is a structure theorem where we show that any
equivariant psd lift of size d of an orbitope is of sum-of-squares type where
the functions in the sum-of-squares decomposition come from an invariant
subspace of dimension smaller than d^3. We use this framework to study two
well-known families of polytopes, namely the parity polytope and the cut
polytope, and we prove exponential lower bounds for equivariant psd lifts of
these polytopes.Comment: v2: 30 pages, Minor changes in presentation; v3: 29 pages, New
structure theorem for general orbitopes + changes in presentatio
Nonuniversal finite-size scaling in anisotropic systems
We study the bulk and finite-size critical behavior of the O symmetric
theory with spatially anisotropic interactions of non-cubic symmetry
in dimensions. In such systems of a given universality class,
two-scale factor universality is absent in bulk correlation functions, and
finite-size scaling functions including the Privman-Fisher scaling form of the
free energy, the Binder cumulant ratio and the Casimir amplitude are shown to
be nonuniversal. In particular it is shown that, for anisotropic confined
systems, isotropy cannot be restored by an anisotropic scale transformation.Comment: 8 pages, 1 figure, accepted for publication in Phys. Rev. E and
modifications of tex
From research data repositories to virtual research environments: a case study from the Humanities
The difference in scholarly practices between the sciences and the mainstream humanities is highlighted in a study (Palmer et al., 2009), which investigated the types of information source materials used in different humanities disciplines, based on results contained in the US Research Libraries Group (RLG) reports. Structured data is relatively little used, except in some areas of historical research, and data as it is traditionally understood in the sciences, i.e. the results of measurements and the lowest level of abstraction for the generation of scientific knowledge, even less so. It is true that the study is partly outdated, containing results from the early 1990s, and that data in the traditional sense is becoming increasingly important in the humanities, particularly for disciplines such as linguistics and archaeology in which scientific techniques have been widely adopted. Nevertheless, it is clear that in general humanities research relies not on measurements as a source of authority, but rather on the provenance of sources and assessment by peers, and that what data repositories are for the sciences, archives are for the humanities. [...
Matchmaking for covariant hierarchies
We describe a model of matchmaking suitable for the implementation of services, rather than their for their discovery and composition. In the model, processing requirements are modelled by client requests and computational resources are software processors that compete for request processing as the covariant implementations of an open service interface. Matchmaking then relies on type analysis to rank processors against requests in support of a wide range of dispatch strategies. We relate the model to the autonomicity of service provision and briefly report on its deployment within a production-level infrastructure for scientic computing
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