17,710 research outputs found
The influence of service temperature on bond between FRP reinforcement and concrete
The interest in fibre reinforced polymer (FRP) reinforcement in construction has considerably increased and especially the application of FRP as externally bonded reinforcement (FRP EBR) has become more and more established. The use of FRP EBR has been adopted world-wide as a very attractive technique for
structural strengthening and rehabilitation. At Ghent university, the fire behaviour of slabs and beams strengthened with advanced composites, including the use of fire protection systems, has been investigated. In addition, the behaviour of the FRP-concrete interface at increased temperatures has been
considered, as elevated temperatures may occur during service conditions, especially for outdoor applications. According to fib Bulletin 14, the glass transition temperature of the adhesive used to bond the FRP should equal 20°C in excess of the maximum ambient temperature at normal service conditions,
and should be at least 45°C. When reaching the glass transition temperature, the properties of the adhesive decrease to a large extend and bond interaction between the concrete and the external FRP reinforcement may be completely lost.
To study the bond behaviour at elevated temperatures, a joint test program between the Universities of Ghent and Lecce has been executed, comprising a series of 20 bond tests performed at the Magnel Laboratory for Concrete Research. The present paper will discuss the experimental work and the main test results obtained
Self-Stabilizing TDMA Algorithms for Dynamic Wireless Ad-hoc Networks
In dynamic wireless ad-hoc networks (DynWANs), autonomous computing devices
set up a network for the communication needs of the moment. These networks
require the implementation of a medium access control (MAC) layer. We consider
MAC protocols for DynWANs that need to be autonomous and robust as well as have
high bandwidth utilization, high predictability degree of bandwidth allocation,
and low communication delay in the presence of frequent topological changes to
the communication network. Recent studies have shown that existing
implementations cannot guarantee the necessary satisfaction of these timing
requirements. We propose a self-stabilizing MAC algorithm for DynWANs that
guarantees a short convergence period, and by that, it can facilitate the
satisfaction of severe timing requirements, such as the above. Besides the
contribution in the algorithmic front of research, we expect that our proposal
can enable quicker adoption by practitioners and faster deployment of DynWANs
that are subject changes in the network topology
Clustering by soft-constraint affinity propagation: Applications to gene-expression data
Motivation: Similarity-measure based clustering is a crucial problem
appearing throughout scientific data analysis. Recently, a powerful new
algorithm called Affinity Propagation (AP) based on message-passing techniques
was proposed by Frey and Dueck \cite{Frey07}. In AP, each cluster is identified
by a common exemplar all other data points of the same cluster refer to, and
exemplars have to refer to themselves. Albeit its proved power, AP in its
present form suffers from a number of drawbacks. The hard constraint of having
exactly one exemplar per cluster restricts AP to classes of regularly shaped
clusters, and leads to suboptimal performance, {\it e.g.}, in analyzing gene
expression data. Results: This limitation can be overcome by relaxing the AP
hard constraints. A new parameter controls the importance of the constraints
compared to the aim of maximizing the overall similarity, and allows to
interpolate between the simple case where each data point selects its closest
neighbor as an exemplar and the original AP. The resulting soft-constraint
affinity propagation (SCAP) becomes more informative, accurate and leads to
more stable clustering. Even though a new {\it a priori} free-parameter is
introduced, the overall dependence of the algorithm on external tuning is
reduced, as robustness is increased and an optimal strategy for parameter
selection emerges more naturally. SCAP is tested on biological benchmark data,
including in particular microarray data related to various cancer types. We
show that the algorithm efficiently unveils the hierarchical cluster structure
present in the data sets. Further on, it allows to extract sparse gene
expression signatures for each cluster.Comment: 11 pages, supplementary material:
http://isiosf.isi.it/~weigt/scap_supplement.pd
Ferromagnetic ordering in graphs with arbitrary degree distribution
We present a detailed study of the phase diagram of the Ising model in random
graphs with arbitrary degree distribution. By using the replica method we
compute exactly the value of the critical temperature and the associated
critical exponents as a function of the minimum and maximum degree, and the
degree distribution characterizing the graph. As expected, there is a
ferromagnetic transition provided < \infty. However, if the fourth
moment of the degree distribution is not finite then non-trivial scaling
exponents are obtained. These results are analyzed for the particular case of
power-law distributed random graphs.Comment: 9 pages, 1 figur
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