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Potsdam, Germany

Ser-Giacomi E.,University of the Balearic Islands | Vasile R.,Ambrosys GmbH | Recuerda I.,University of the Balearic Islands | Hernandez-Garcia E.,University of the Balearic Islands | Lopez C.,University of the Balearic Islands
Chaos | Year: 2015

Eastern Europe and Western Russia experienced a strong heat wave with devastating consequences in the summer of 2010. This was due to an atmospheric blocking episode that lasted during several weeks. Despite these types of events have been well-investigated over the years, a complete understanding and prediction is still missing. In this work, we present a characterization of this flow pattern based on the study of fluid transport as a Lagrangian flow network, so that the methodology of complex networks can be applied. In particular, the most probable paths (MPPs) linking nodes of this atmospheric network reveal the dominant pathways traced by atmospheric fluid particles.

Stefanakis N.,University of Potsdam | Abel M.,Ambrosys GmbH | Bergner A.,Native Instruments GmbH
Computer Music Journal | Year: 2015

Ordinary differential equations (ODEs) have been studied for centuries as a means to model complex dynamical processes from the real world. Nevertheless, their application to sound synthesis has not yet been fully exploited. In this article we present a systematic approach to sound synthesis based on first-order complex and real ODEs. Using simple time-dependent and nonlinear terms, we illustrate the mapping between ODE coefficients and physically meaningful control parameters such as pitch, pitch bend, decay rate, and attack time. We reveal the connection between nonlinear coupling terms and frequency modulation, and we discuss the implications of this scheme in connection with nonlinear synthesis. The ability to excite a first-order complex ODE with an external input signal is also examined; stochastic or impulsive signals that are physically or synthetically produced can be presented as input to the system, offering additional synthesis possibilities, such as those found in excitation/filter synthesis and filter-based modal synthesis. © 2015 Massachusetts Institute of Technology.

Winkler M.,University of Potsdam | Abel M.,University of Potsdam | Abel M.,Ambrosys GmbH
Review of Scientific Instruments | Year: 2016

We present a novel experimental setup to investigate two-dimensional thermal convection in a freestanding thin liquid film. Such films can be produced in a controlled way on the scale of 5-1000 nm. Our primary goal is to investigate convection patterns and the statistics of reversals in Rayleigh-Bénard convection with varying aspect ratio. Additionally, questions regarding the physics of liquid films under controlled conditions can be investigated, like surface forces, or stability under varying thermodynamical parameters. The film is suspended in a frame which can be adjusted in height and width to span an aspect ratio range of Γ = 0.16-10. The top and bottom frame elements can be set to specific temperature within T = 15 °C to 55 °C. A thickness to area ratio of approximately 108 enables only two-dimensional fluid motion in the time scales relevant for turbulent motion. The chemical composition of the film is well-defined and optimized for film stability and reproducibility and in combination with carefully controlled ambient parameters allows the comparison to existing experimental and numerical data. © 2016 Author(s).

Winkler M.,University of Potsdam | Abel M.,University of Potsdam | Abel M.,Ambrosys GmbH
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We study aqueous, freestanding, thin films stabilized by a surfactant with respect to mixing and dynamical systems properties. With this special setup, a two-dimensional fluid can be realized experimentally. The physics of the system involves a complex interplay of thermal convection and interface and gravitational forces. Methodologically, we characterize the system using two classical dynamical systems properties: Lyapunov exponents and entropies. Our experimental setup produces convection with two stable eddies by applying a temperature gradient in one spot that yields weakly turbulent mixing. From dynamical systems theory, one expects a relation of entropies, Lyapunov exponents, a prediction with little experimental support. We can confirm the corresponding statements experimentally, on different scales using different methods. On the small scale the motion and deformation of fluid filaments of equal size (color imaging velocimetry) are used to compute Lyapunov exponents. On the large scale, entropy is computed by tracking the left-right motion of the center fluid jet at the separatrix between the two convection rolls. We thus combine here dynamical systems methods with a concrete application of mixing in a nanoscale freestanding thin film. © 2015 American Physical Society.

Ser-Giacomi E.,Institute Fisica Interdisciplinar y Sistemas Complejos CSIC UIB | Vasile R.,Institute Fisica Interdisciplinar y Sistemas Complejos CSIC UIB | Vasile R.,Ambrosys GmbH | Hernandez-Garcia E.,Institute Fisica Interdisciplinar y Sistemas Complejos CSIC UIB | Lopez C.,Institute Fisica Interdisciplinar y Sistemas Complejos CSIC UIB
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We consider paths in weighted and directed temporal networks, introducing tools to compute sets of paths of high probability. We quantify the relative importance of the most probable path between two nodes with respect to the whole set of paths and to a subset of highly probable paths that incorporate most of the connection probability. These concepts are used to provide alternative definitions of betweenness centrality. We apply our formalism to a transport network describing surface flow in the Mediterranean sea. Despite the full transport dynamics is described by a very large number of paths we find that, for realistic time scales, only a very small subset of high probability paths (or even a single most probable one) is enough to characterize global connectivity properties of the network. © 2015 American Physical Society.

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