TY - JOUR A1 - Bube, Kevin A1 - Neto, Camilo Rodrigues A1 - Donner, Reik Volker A1 - Schwarz, Udo A1 - Feudel, Ulrike T1 - Linear and nonlinear characterization of surfaces from a laser beam melt ablation process N2 - 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 Y1 - 2006 UR - http://iopscience.iop.org/0022-3727/ U6 - https://doi.org/10.1088/0022-3727/39/7/011 SN - 0022-3727 ER - TY - JOUR A1 - Komalapriya, Chandrasekaran A1 - Romano Blasco, Maria Carmen A1 - Thiel, Marco A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Simonotto, Jennifer A1 - Furman, Michael A1 - Ditto, William L. A1 - Carney, Paul R. T1 - Analysis of high-resulution microelectrode EEG recordings in an animal model of spontaneous limbic seizures Y1 - 2009 UR - http://www.worldscinet.com/ijbc/ijbc.shtml U6 - https://doi.org/10.1142/S0218127409023226 SN - 0218-1274 ER - TY - JOUR A1 - Kurths, Jürgen A1 - Schwarz, Udo T1 - Application of techniques of nonlinear dynamics to SS Cyg N2 - We look for structural properties in the light curve of the dwarf nova SS Cyg by means of techniques from nonlinear dynamics. Applying the popular Grassberger-Procaccia procedure, Cannizzo and Goddings (1988) showed that there is no evidence for a low-dimensional attractor underlying this record. Because there are some hints for order in the light curve, we search for other signatures of deterministic systems. Therefore, we use other methods recently developed in this theory, such as local linear prediction and recurrence maps. Our main findings are: i] the prediction error grows exponentially during outburst phases, but via a power law in the quiescent states, ii] there are some rather regular patterns in this light curve which sometimes recur, but the recurrence is not regular. This leads to the following conclusions: i] The outburst dynamics shows a higher degree of order than the quiescent one. There are some hints for deterministic chaos in the outburst behavior. ii] The light curve is a complex mixture of deterministic and stochastic structures. The analysis presented in this paper shows that methods of nonlinear dynamics can be an efficient tool for the study of complex processes, even if there is no evidence for a low-dimensional attractor. Y1 - 1993 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/SS_Cyg_AIP.ps.gz SN - 0-7503-0282-8 ER - TY - THES A1 - Schwarz, Udo T1 - Zeitreihenanalyse astrophysikalischer Aktivitätsphänomene Y1 - 1994 ER - TY - JOUR A1 - Kurths, Jürgen A1 - Schwarz, Udo A1 - Parlitz, Ulrich A1 - Sonett, Charles P. T1 - Testing for nonlinearity in radiocarbon data N2 - The radiocarbon record that has been extended from 7199 BC to 1891 AD is of fundamental importance to understand century-scale variations of solar activity. We have, therefore, studied how to extract information from dynamic reconstructions of this observational record. Using some rather unusual methods of nonlinear dynamics, we have found that the data are significantly different from linear colored noise and that there is some evidence of nonlinear behavior. The method of recurrence plots exhibits that the grand minima of solar activity are quite different in their recurrence. Most remarkably, it suggests that the recent epoch seems to be similar to the Medieval maximum. Y1 - 1994 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/n.ps.gz SN - 1023-5809 ER - TY - JOUR A1 - Kurths, Jürgen A1 - Schwarz, Udo T1 - Chaos theory and radio emission N2 - The application of chaos theory has become popular to understand the nature of various features of solar activity because most of them are far from regular. The usual approach, however, that is basing on finding low- dimensional structures of the underlying processes seems to be successful only in a few exceptional cases, such as in rather coherent phenomena as coronal pulsations. It is important to note that most phenomena in solar radio emission are more complex. We present two kinds of techniques from nonlinear dynamics which can be useful to analyse such phenomena: i] Fragmentation processes observed in solar spike events are studied by means of symbolic dynamics methods. Different measures of complexity calculated from such observations reveal that there is some order in this fragmentation. ii] Bursts are a typical transient phenomenon. To study energization processes causing impulsive microwave bursts, the wavelet analysis is applied. It exhibits structural differences of the pre- and post-impulsive phase in cases where the power spectra of both are not distinct. Y1 - 1994 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/Review.ps.gz ER - TY - JOUR A1 - Schwarz, Udo T1 - Das Maunder-Minimum : alles sonnenklar, oder? N2 - Im vorletzten Absatz des o.g. Kurzberichtes befindet sich eine falsche Aussage zur C14-Produktion waehrend des Maunder-Minimums. Wie aus der in meiner Abbildung gezeigten Delta C14-Haeufigkeit fuer den Zeitraum des Maunder-Minimums hervorgeht, war die C14-Produktion zu dieser Zeit erhoeht statt, wie von Herrn Buehrke und anderen Autoren in der Literatur behauptet, erniedrigt. Die allgemein akzeptierte Begruendung fuer die erhoehte C14-Produktion lautet: Der geringere Sonnenwind schirmt die Erde weniger stark von der kosmischen Strahlung ab. Y1 - 1994 ER - TY - JOUR A1 - Kurths, Jürgen A1 - Schwarz, Udo A1 - Witt, Annette T1 - Non-linear data analysis in solar radio astronomy N2 - We have discussed some tools from nonlinear dynamics which may help to analyze transient phenomena, such as solar bursts. The structure function known from turbulence theory is an appropriate method to find out some scaling behavior of fluctuations in time. More generally, the wavelet analysis, which is some generalization of the power spectrum, exhibits information on the location as well as the size of hidden characteristic features. Applying both techniques to microwave bursts, we have found some scaling properties that refer to the existence of hierarchic time structures. This is in good accordance with the electric circuit model for describing the flare-particle energization process. Y1 - 1995 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/lnp.ps.gz ER - TY - BOOK A1 - Voss, Henning U. A1 - Kurths, Jürgen A1 - Schwarz, Udo T1 - Reconstruction of grand minima of solar activity from radiocarbon data : linear and nonlinear signal analysis T3 - Preprint NLD Y1 - 1996 VL - 28 PB - Univ. CY - Potsdam ER - TY - JOUR A1 - Voss, Henning U. A1 - Kurths, Jürgen A1 - Schwarz, Udo T1 - Reconstruction of grand minima of solar activity from radiocarbon data : linear and nonlinear signal analysis N2 - Using a special technique of data analysis, we have found out 34 grand minima of solar activity in a 7,700 years long C14 record. The method used rests on a proper filtering of the C14 record and the extrapolation of verifiable results for the later history back in time. Additionally, we have applied a method of nonlinear dynamics, the recurrence rate, to back up the results. Our findings are not contradictory to the record of grand minima by Eddy, but constitute a considerable extension. Hence, it has become possible to look closer at the validity of models. This way, we have tested esp. the model of Barnes et al. There are hints for that the grand minima might solely be driven by the 209--year period found in the C14 record. Y1 - 1996 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/vks.ps.gz ER -