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DDC: 500 × Has files: Yes × Type: Text × Version: publishedVersion × WGL Institute: PIK ×

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Now showing 1 - 10 of 280
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    Nachhaltiges Wassermanagement in einer globalisierten Welt : Schlussbericht ; Laufzeit des Vorhabens: 01.04.2010 - 31.06.2013
    (Hannover : Technische Informationsbibliothek, 2013) Biewald, Anne
    [no abstract available]
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    Entdecken: Entwicklung und Dekarbonisierung in Entwicklungs- und Schwellenländern : Schlussbericht ; Laufzeit des Vorhabens: 01.08.2010 - 31.10.2013
    (Hannover : Technische Informationsbibliothek, 2013) Edenhofer, Ottmar
    [no abstract available]
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    Wirkung von Klimaänderungen auf Vegetation: Entwicklung eines allgemeinen Modells für die Klimafolgenforschung : Abschlußbericht
    (Potsdam : Potsdam-Institut für Klimaforschung, 1999) Cramer, Wolfgang
    [no abstract available]
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    Survivability of deterministic dynamical systems
    (London : Nature Publishing Group, 2016) Hellmann, Frank; Schultz, Paul; Grabow, Carsten; Heitzig, Jobst; Kurths, Jürgen
    The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures.
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    Universality in spectral condensation
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2020) Pavithran, Induja; Unni, Vishnu R.; Varghese, Alan J.; Premraj, D.; Sujith, R. I.; Vijayan, C.; Saha, Abhishek; Marwan, Norbert; Kurths, Jürgen
    Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomenon. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems.
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    Dynamic Network Characteristics of Power-electronics-based Power Systems
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2020) Ji, Yuxi; He, Wei; Cheng, Shijie; Kurths, Jürgen; Zhan, Meng
    Power flow studies in traditional power systems aim to uncover the stationary relationship between voltage amplitude and phase and active and reactive powers; they are important for both stationary and dynamic power system analysis. With the increasing penetration of large-scale power electronics devices including renewable generations interfaced with converters, the power systems become gradually power-electronics-dominant and correspondingly their dynamical behavior changes substantially. Due to the fast dynamics of converters, such as AC current controller, the quasi-stationary state approximation, which has been widely used in power systems, is no longer appropriate and should be reexamined. In this paper, for a better description of network characteristics, we develop a novel concept of dynamic power flow and uncover an explicit dynamic relation between the instantaneous powers and the voltage vectors. This mathematical relation has been well verified by simulations on transient analysis of a small power-electronics-based power system, and a small-signal frequency-domain stability analysis of a voltage source converter connected to an infinitely strong bus. These results demonstrate the applicability of the proposed method and shed an improved light on our understanding of power-electronics-dominant power systems, whose dynamical nature remains obscure.
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    Future tree survival in European forests depends on understorey tree diversity
    (London : Nature Publishing Group, 2022) Billing, Maik; Thonicke, Kirsten; Sakschewski, Boris; Bloh, Werner von; Walz, Ariane
    Climate change heavily threatens forest ecosystems worldwide and there is urgent need to understand what controls tree survival and forests stability. There is evidence that biodiversity can enhance ecosystem stability (Loreau and de Mazancourt in Ecol Lett 16:106–115, 2013; McCann in Nature 405:228–233, 2000), however it remains largely unclear whether this also holds for climate change and what aspects of biodiversity might be most important. Here we apply machine learning to outputs of a flexible-trait Dynamic Global Vegetation Model to unravel the effects of enhanced functional tree trait diversity and its sub-components on climate-change resistance of temperate forests (http://www.pik-potsdam.de/~billing/video/Forest_Resistance_LPJmLFIT.mp4). We find that functional tree trait diversity enhances forest resistance. We explain this with 1. stronger complementarity effects (~ 25% importance) especially improving the survival of trees in the understorey of up to + 16.8% (± 1.6%) and 2. environmental and competitive filtering of trees better adapted to future climate (40–87% importance). We conclude that forests containing functionally diverse trees better resist and adapt to future conditions. In this context, we especially highlight the role of functionally diverse understorey trees as they provide the fundament for better survival of young trees and filtering of resistant tree individuals in the future.
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    Study of the Atlantic thermohaline circulation in a highly efficient global ocean-atmosphere model : final report for the project CLIVAR
    (Hannover : Technische Informationsbibliothek, 2002) Rahmstorf, Stefan; Ganopolsky, Andrey; Morals Maqueda, Miguel A.
    [no abstract available]
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    CLME - Eine Version des regionalen Modells CLM für die Simulation von extremen Ereignissen : Schlussbericht
    (Hannover : Technische Informationsbibliothek, 2008) Klein, R.; Gerstengarbe, Friedrich-Wilhelm
    [no abstract available]