26,922 research outputs found
A Three-Step Methodology to Improve Domestic Energy Efficiency
Increasing energy prices and the greenhouse effect lead to more awareness of energy efficiency of electricity supply. During the last years, a lot of technologies have been developed to improve this efficiency. Next to large scale technologies such as windturbine parks, domestic technologies are developed. These domestic technologies can be divided in 1) Distributed Generation (DG), 2) Energy Storage and 3) Demand Side Load Management. Control algorithms optimizing a combination of these techniques can raise the energy reduction potential of the individual techniques. In this paper an overview of current research is given and a general concept is deducted. Based on this concept, a three-step optimization methodology is proposed using 1) offline local prediction, 2) offline global planning and 3) online local scheduling. The paper ends with results of simulations and field tests showing that the methodology is promising.\u
Tensor Product Approximation (DMRG) and Coupled Cluster method in Quantum Chemistry
We present the Copupled Cluster (CC) method and the Density matrix
Renormalization Grooup (DMRG) method in a unified way, from the perspective of
recent developments in tensor product approximation. We present an introduction
into recently developed hierarchical tensor representations, in particular
tensor trains which are matrix product states in physics language. The discrete
equations of full CI approximation applied to the electronic Schr\"odinger
equation is casted into a tensorial framework in form of the second
quantization. A further approximation is performed afterwards by tensor
approximation within a hierarchical format or equivalently a tree tensor
network. We establish the (differential) geometry of low rank hierarchical
tensors and apply the Driac Frenkel principle to reduce the original
high-dimensional problem to low dimensions. The DMRG algorithm is established
as an optimization method in this format with alternating directional search.
We briefly introduce the CC method and refer to our theoretical results. We
compare this approach in the present discrete formulation with the CC method
and its underlying exponential parametrization.Comment: 15 pages, 3 figure
Synchronization and modularity in complex networks
We investigate the connection between the dynamics of synchronization and the
modularity on complex networks. Simulating the Kuramoto's model in complex
networks we determine patterns of meta-stability and calculate the modularity
of the partition these patterns provide. The results indicate that the more
stable the patterns are, the larger tends to be the modularity of the partition
defined by them. This correlation works pretty well in homogeneous networks
(all nodes have similar connectivity) but fails when networks contain hubs,
mainly because the modularity is never improved where isolated nodes appear,
whereas in the synchronization process the characteristic of hubs is to have a
large stability when forming its own community.Comment: To appear in the Proceedings of Workshop on Complex Systems: New
Trends and Expectations, Santander, Spain, 5-9 June 200
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