Self-organized flows in phase-synchronizing active fluids

Many active biological particles, such as swimming microorganisms or motor-proteins, do work on their environment by going though a periodic sequence of shapes. Interactions between particles can lead to the phase-synchronization of their duty cycles. Here we consider collective dynamics in a suspension of such active particles coupled through hydrodynamics. We demonstrate that the emergent non-equilibrium states feature stationary patterned flows and robust unidirectional pumping states under confinement. Moreover the phase-synchronized state of the suspension exhibits spatially robust chimera patterns in which synchronized and phase-isotropic regions coexist within the same system. These findings demonstrate a new route to pattern formation and could guide the design of new active materials.Comment: 6 pages, 3 figure

Stability Analysis and Clustering of Electrical Transmission Systems

A proper understanding and modelling of the behaviour of heavily loaded large-scale electrical transmission systems is essential for a secure and uninterrupted operation. In this paper we present a descriptive analysis especially of low frequency oscillations within an electricity network and methods to assess the stability of the whole system based on an ARMAX model and the ESPRIT algorithm. Further we present two methods to separate the network into local areas, which is necessary for an efficient modelling of a large electrical system. The first method has its foundation in the results of the ARMAX based stability analysis and the second method concentrates on the network topology. In the last part of this paper we present an approach how an modelling of such local areas within an large electrical system based on stochastic differential equation models is possible

Technical Report for Research Unit FOR-1511

This technical report presents the interim results of the DFG research unit FOR1511 "Protection and Control Systems for Reliable and Secure Operation of Electrical Transmission Systems"