@article{BaumbachSiegmundMittermeieretal.2017,
  author    = {Baumbach, Lukas and Siegmund, Jonatan F. and Mittermeier, Magdalena and Donner, Reik Volker},
  title     = {Impacts of temperature extremes on European vegetation during the growing season},
  series = {Biogeosciences},
  volume    = {14},
  journal   = {Biogeosciences},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1726-4170},
  doi       = {10.5194/bg-14-4891-2017},
  pages     = {4891 -- 4903},
  year      = {2017},
  abstract  = {Temperature is a key factor controlling plant growth and vitality in the temperate climates of the mid-latitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies (LSTAD) and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.},
  language  = {en}
}
@book{DonnerCserSchwarzetal.2004,
  author    = {Donner, Reik Volker and Cser, Adrienn and Schwarz, Udo and Otto, Andreas H. and Feudel, Ulrike},
  title     = {An approach to a process model of laser beam melt ablation using methods of linear and non-linear data analysis},
  isbn      = {3-527-40430-9},
  year      = {2004},
  abstract  = {As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.},
  language  = {en}
}
@book{DonnerCserSchwarzetal.2003,
  author    = {Donner, Reik Volker and Cser, Adrienn and Schwarz, Udo and Otto, Andreas H. and Feudel, Ulrike},
  title     = {An approach to a process model of laser beam melt ablation using methods of linear and non-linear data analysis},
  isbn      = {3-928921-88-6},
  year      = {2003},
  abstract  = {As a non-contact process laser beam melt ablation offers several advantages compared to conventional processing mechanisms. During ablation the surface of the workpiece is molten by the energy of a CO2-laser beam, this melt is then driven out by the impulse of an additional process gas. Although the idea behind laser beam melt ablation is rather simple, the process itself has a major limitation in practical applications: with increasing ablation rate surface quality of the workpiece processed declines rapidly. With different ablation rates different surface structures can be distinguished, which can be characterised by suitable surface parameters. The corresponding regimes of pattern formation are found in linear and non-linear statistical properties of the recorded process emissions as well. While the ablation rate can be represented in terms of the line-energy, this parameter does not provide sufficient information about the full behaviour of the system. The dynamics of the system is dominated by oscillations due to the laser cycle but includes some periodically driven non-linear processes as well. Upon the basis of the measured time series, a corresponding model is developed. The deeper understanding of the process can be used to develop strategies for a process control.},
  language  = {en}
}
@article{CserDonnerSchwarzetal.2002,
  author    = {Cser, Adrienn and Donner, Reik Volker and Schwarz, Udo and Otto, Andreas H. and Geiger, M. and Feudel, Ulrike},
  title     = {Towards a better understanding of laser beam melt ablation using methods of statistical analysis},
  isbn      = {88-87030-44-8},
  year      = {2002},
  abstract  = {Laser beam melt ablation, as a contact free machining process, offers several advantages compared to conventional processing mechanisms. Although the idea behind it is rather simple, the process has a major limitation: with increasing ablation rate surface quality of the workpiece processed declines rapidly. The structures observed show a clear dependence of the line energy. In dependence of this parameter several regimes of the process have been separated. These are clearly distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions which is the observed quantity chosen.},
  language  = {en}
}
@article{DonnerSeehaferSanjuanetal.2006,
  author    = {Donner, Reik Volker and Seehafer, Norbert and Sanjuan, Miguel Angel Fernandez and Feudel, Fred},
  title     = {Low-dimensional dynamo modelling and symmetry-breaking bifurcations},
  series = {Physica. D, Nonlinear phenomena},
  volume    = {223},
  journal   = {Physica. D, Nonlinear phenomena},
  number    = {2},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2006.08.022},
  pages     = {151 -- 162},
  year      = {2006},
  abstract  = {Motivated by the successful Karlsruhe dynamo experiment, a relatively low-dimensional dynamo model is proposed. It is based on a strong truncation of the magnetohydrodynamic (MHD) equations with an external forcing of the Roberts type and the requirement that the model system satisfies the symmetries of the full MHD system, so that the first symmetry-breaking bifurcations can be captured. The backbone of the Roberts dynamo is formed by the Roberts flow, a helical mean magnetic field and another part of the magnetic field coupled to these two by triadic mode interactions. A minimum truncation model (MTM) containing only these energetically dominating primary mode triads is fully equivalent to the widely used first-order smoothing approximation. However, it is shown that this approach works only in the limit of small wave numbers of the excited magnetic field or small magnetic Reynolds numbers (\$Rm ll 1\$). To obtain dynamo action under more general conditions, secondary mode},
  language  = {en}
}
@article{DonnerFeudelSeehaferetal.2007,
  author    = {Donner, Reik Volker and Feudel, Fred and Seehafer, Norbert and Sanjuan, Miguel Angel Fernandez},
  title     = {Hierarchical modeling of a forced Roberts Dynamo},
  issn      = {0218-1274},
  doi       = {10.1142/S021812740701941X},
  year      = {2007},
  abstract  = {We investigate the dynamo effect in a flow configuration introduced by G. O. Roberts in 1972. Based on a clear energetic hierarchy of Fourier components on the steady-state dynamo branch, an approximate model of interacting modes is constructed covering all essential features of the complete system but allowing simulations with a minimum amount of computation time. We use this model to study the excitation mechanism of the dynamo, the transition from stationary to time-dependent dynamo solutions and the characteristic properties of the latter ones.},
  language  = {en}
}
@article{BubeNetoDonneretal.2006,
  author    = {Bube, Kevin and Neto, Camilo Rodrigues and Donner, Reik Volker and Schwarz, Udo and Feudel, Ulrike},
  title     = {Linear and nonlinear characterization of surfaces from a laser beam melt ablation process},
  issn      = {0022-3727},
  doi       = {10.1088/0022-3727/39/7/011},
  year      = {2006},
  abstract  = {We apply linear and nonlinear methods to study the properties of surfaces generated by a laser beam melt ablation process. As a result we present a characterization and ordering of the surfaces depending on the adjusted process parameters. Our findings give some insight into the performance of two widely applied multifractal analysis methods-the detrended fluctuation analysis and the wavelet transform modulus maxima method-on short real world data},
  language  = {en}
}
@misc{SiegmundSandersHeinrichetal.2016,
  author    = {Siegmund, Jonatan Frederik and Sanders, Tanja G. M. and Heinrich, Ingo and Maaten, Ernst van der and Simard, Sonia and Helle, Gerhard and Donner, Reik Volker},
  title     = {Meteorological drivers of extremes in daily stem radius variations of beech, oak, and pine in Northeastern Germany},
  series = {Frontiers in plant science},
  journal   = {Frontiers in plant science},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407943},
  pages     = {14},
  year      = {2016},
  abstract  = {Observed recent and expected future increases in frequency and intensity of climatic extremes in central Europe may pose critical challenges for domestic tree species. Continuous dendrometer recordings provide a valuable source of information on tree stem radius variations, offering the possibility to study a tree's response to environmental influences at a high temporal resolution. In this study, we analyze stem radius variations (SRV) of three domestic tree species (beech, oak, and pine) from 2012 to 2014. We use the novel statistical approach of event coincidence analysis (ECA) to investigate the simultaneous occurrence of extreme daily weather conditions and extreme SRVs, where extremes are defined with respect to the common values at a given phase of the annual growth period. Besides defining extreme events based on individual meteorological variables, we additionally introduce conditional and joint ECA as new multivariate extensions of the original methodology and apply them for testing 105 different combinations of variables regarding their impact on SRV extremes. Our results reveal a strong susceptibility of all three species to the extremes of several meteorological variables. Yet, the inter-species differences regarding their response to the meteorological extremes are comparatively low. The obtained results provide a thorough extension of previous correlation-based studies by emphasizing on the timings of climatic extremes only. We suggest that the employed methodological approach should be further promoted in forest research regarding the investigation of tree responses to changing environmental conditions.},
  language  = {en}
}
@article{SiegmundSandersHeinrichetal.2016,
  author    = {Siegmund, Jonatan F. and Sanders, Tanja G. M. and Heinrich, Ingo and van der Maaten, Ernst and Simard, Sonia and Helle, Gerhard and Donner, Reik Volker},
  title     = {Meteorological Drivers of Extremes in Daily Stem Radius Variations of Beech, Oak, and Pine in Northeastern Germany: An Event Coincidence Analysis},
  series = {Frontiers in plant science},
  volume    = {7},
  journal   = {Frontiers in plant science},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {1664-462X},
  doi       = {10.3389/fpls.2016.00733},
  pages     = {4701 -- 4712},
  year      = {2016},
  abstract  = {Observed recent and expected future increases in frequency and intensity of climatic extremes in central Europe may pose critical challenges for domestic tree species. Continuous dendrometer recordings provide a valuable source of information on tree stem radius variations, offering the possibility to study a tree's response to environmental influences at a high temporal resolution. In this study, we analyze stem radius variations (SRV) of three domestic tree species (beech, oak, and pine) from 2012 to 2014. We use the novel statistical approach of event coincidence analysis (ECA) to investigate the simultaneous occurrence of extreme daily weather conditions and extreme SRVs, where extremes are defined with respect to the common values at a given phase of the annual growth period. Besides defining extreme events based on individual meteorological variables, we additionally introduce conditional and joint ECA as new multivariate extensions of the original methodology and apply them for testing 105 different combinations of variables regarding their impact on SRV extremes. Our results reveal a strong susceptibility of all three species to the extremes of several meteorological variables. Yet, the inter-species differences regarding their response to the meteorological extremes are comparatively low. The obtained results provide a thorough extension of previous correlation-based studies by emphasizing on the timings of climatic extremes only. We suggest that the employed methodological approach should be further promoted in forest research regarding the investigation of tree responses to changing environmental conditions.},
  language  = {en}
}
@article{CserDonnerSchwarzetal.2001,
  author    = {Cser, Adrienn and Donner, Reik Volker and Schwarz, Udo and Feudel, Ulrike and Otto, Andreas H.},
  title     = {Statistical parameters of a control strategy of laser beam melt ablation},
  year      = {2001},
  abstract  = {Laser beam melt ablation - a contact-free machining process - offers several advantages compared to conventional processing mechanisms: there exists no tool wear and even extremely hard or brittle materials can be processed. During ablation the workpiece is molten by a CO2-laser beam, this melt is then driven out by the impulse of a process gas. The idea behind laser ablation is rather simple, but it has a major limitation in practical applications: with increasing ablation rates surface quality of the workpiece processed declines rapidly. At high ablation rates, depending on the process parameters different periodic-like structures can be observed on the ablated surface. These structures show a dependence on the line energy, which has been identified as a fundamental control parameter. In dependence on this parameter several regimes with different behaviours of the process have been separated. These regimes are distinguishable as well in the surfaces obtained as in the signals gained by the measurement of the process emissions. Further aim is to identify the different modes of the system and reach a deeper understanding of the dynamics of the molten material in order to understand the formation of these surface structures. With this it should be possible to influence the system in the direction of avoiding structure formation even at high ablation rates. Relying on the results on-line monitoring and control of the process should be studied.},
  language  = {en}
}