3,253 research outputs found
An effective local routing strategy on the BA network
In this paper, We propose a effective routing strategy on the basis of the
so-called nearest neighbor search strategy by introducing a preferential
delivering exponent alpha. we assume that the handling capacity of one vertex
is proportional to its degree when the degree is smaller than a cut-off value
, and is infinite otherwise. It is found that by tuning the parameter alpha,
the scale-free network capacity measured by the order parameter is considerably
enhanced compared to the normal nearest-neighbor strategy. Traffic dynamics
both near and far away from the critical generating rate R_c are discussed. We
also investigate R_c as functions of m (connectivity density), K (cutoff
value). Due to the low cost of acquiring nearest-neighbor information and the
strongly improved network capacity, our strategy may be useful and reasonable
for the protocol designing of modern communication networks.Comment: 9 pages, 5 figure
Phase transitions on heterogeneous random graphs: some case studies
The focus of this thesis is about statistical mechanics on heterogeneous
random graphs, i.e. how this heterogeneity affects the cooperative behavior of
model systems. It is not intended as a review on it, rather it is showed how
this question emerges naturally and can give useful insights to specific
instances. The first chapter is about the statistical mechanics of congestion
in queuing networks. The second is devoted to the study of the glassy dynamics
of facilitated spin models on disordered structures. In the third chapter, the
presence of inverse phase transitions in tri-critical spin systems on
heterogeneous random graphs is pointed out. Finally, the last chapter is on the
role of volatility in the evolution of social networks. In the conclusions, a
general insight about the interplay between structure and dynamics on
heterogeneous random graphs is given. It is based on the different scaling of
the transition point with the moments of the degree distribution for continuous
and discontinuous transitions, respectively.Comment: PHD Thesi
Market and Economic Modelling of the Intelligent Grid: End of Year Report 2009
The overall goal of Project 2 has been to provide a comprehensive understanding of the impacts of distributed energy (DG) on the Australian Electricity System. The research team at the UQ Energy Economics and Management Group (EEMG) has constructed a variety of sophisticated models to analyse the various impacts of significant increases in DG. These models stress that the spatial configuration of the grid really matters - this has tended to be neglected in economic discussions of the costs of DG relative to conventional, centralized power generation. The modelling also makes it clear that efficient storage systems will often be critical in solving transient stability problems on the grid as we move to the greater provision of renewable DG. We show that DG can help to defer of transmission investments in certain conditions. The existing grid structure was constructed with different priorities in mind and we show that its replacement can come at a prohibitive cost unless the capability of the local grid to accommodate DG is assessed very carefully.Distributed Generation. Energy Economics, Electricity Markets, Renewable Energy
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"In these pages you will learn about the fascinating research endeavors that each of our faculty members is undertaking. We have divided their research into the broad categories of health, sustainability, information, and systems. While we recognize the imperfect nature of categorizing research that, by its very nature may be interdisciplinary or transdisciplinary, we nonetheless believe it will be helpful as a way to see the depth and breadth of our research endeavors within each grouping. As you read the profiles on these pages, I know you will begin to appreciate that, taken as a whole, the research spectrum at Columbia Engineering is exceptional and that, as our professors go about their work, they are at the cusp of making breakthroughs that will have a major impact on the way we live our lives today and tomorrow.
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