21,057 research outputs found
Correlations and Clustering in Wholesale Electricity Markets
We study the structure of locational marginal prices in day-ahead and
real-time wholesale electricity markets. In particular, we consider the case of
two North American markets and show that the price correlations contain
information on the locational structure of the grid. We study various
clustering methods and introduce a type of correlation function based on event
synchronization for spiky time series, and another based on string correlations
of location names provided by the markets. This allows us to reconstruct
aspects of the locational structure of the grid.Comment: 30 pages, several picture
Detection of Complex Networks Modularity by Dynamical Clustering
Based on cluster de-synchronization properties of phase oscillators, we
introduce an efficient method for the detection and identification of modules
in complex networks. The performance of the algorithm is tested on computer
generated and real-world networks whose modular structure is already known or
has been studied by means of other methods. The algorithm attains a high level
of precision, especially when the modular units are very mixed and hardly
detectable by the other methods, with a computational effort on
a generic graph with nodes and links.Comment: 5 pages, 2 figures. Version accepted for publication on PRE Rapid
Communications: figures changed and text adde
The Parallelism Motifs of Genomic Data Analysis
Genomic data sets are growing dramatically as the cost of sequencing
continues to decline and small sequencing devices become available. Enormous
community databases store and share this data with the research community, but
some of these genomic data analysis problems require large scale computational
platforms to meet both the memory and computational requirements. These
applications differ from scientific simulations that dominate the workload on
high end parallel systems today and place different requirements on programming
support, software libraries, and parallel architectural design. For example,
they involve irregular communication patterns such as asynchronous updates to
shared data structures. We consider several problems in high performance
genomics analysis, including alignment, profiling, clustering, and assembly for
both single genomes and metagenomes. We identify some of the common
computational patterns or motifs that help inform parallelization strategies
and compare our motifs to some of the established lists, arguing that at least
two key patterns, sorting and hashing, are missing
Community structure in real-world networks from a non-parametrical synchronization-based dynamical approach
This work analyzes the problem of community structure in real-world networks
based on the synchronization of nonidentical coupled chaotic R\"{o}ssler
oscillators each one characterized by a defined natural frequency, and coupled
according to a predefined network topology. The interaction scheme contemplates
an uniformly increasing coupling force to simulate a society in which the
association between the agents grows in time. To enhance the stability of the
correlated states that could emerge from the synchronization process, we
propose a parameterless mechanism that adapts the characteristic frequencies of
coupled oscillators according to a dynamic connectivity matrix deduced from
correlated data. We show that the characteristic frequency vector that results
from the adaptation mechanism reveals the underlying community structure
present in the network.Comment: 21 pages, 7 figures; Chaos, Solitons & Fractals (2012
Synchronization and structure in an adaptive oscillator network
We analyze the interplay of synchronization and structure evolution in an
evolving network of phase oscillators. An initially random network is
adaptively rewired according to the dynamical coherence of the oscillators, in
order to enhance their mutual synchronization. We show that the evolving
network reaches a small-world structure. Its clustering coefficient attains a
maximum for an intermediate intensity of the coupling between oscillators,
where a rich diversity of synchronized oscillator groups is observed. In the
stationary state, these synchronized groups are directly associated with
network clusters.Comment: 6 pages, 7 figure
- …