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 - Marwan, Norbert A1 - Trauth, Martin H. A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Strecker, Manfred T1 - Climate dynamics of varved pleistocene lake sediments in nw Argentina Y1 - 1999 SN - 1029-7006 ER - TY - JOUR A1 - Spahn, Frank A1 - Katzorke, Ines A1 - Petzschmann, Olaf A1 - Schwarz, Udo A1 - Kurths, Jürgen T1 - Cluster instabiliy of granular assemblies Y1 - 1997 ER - TY - JOUR A1 - Spahn, Frank A1 - Schwarz, Udo A1 - Kurths, Jürgen T1 - Clustering of granular assemblies with temperature dependent restitution under Keplerian differential rotation Y1 - 1997 ER - TY - JOUR A1 - Marwan, Norbert A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Strecker, Manfred T1 - ENSO Impact on landslide generation in northwestern Argentina N2 - Climatic changes are of major importance in landslide generation in the Argentine Andes. Increased humidity as a potential influential factor was inferred from the temporal clustering of landslide deposits during a period of significantly wetter climate, 30,000 years ago. A change in seasonality was tested by comparing past (inferred from annual-layered lake deposits, 30,000 years old) and modern (present-day observations) precipitation changes. Quantitative analysis of cross recurrence plots were developed to compare the influence of the El Nino/Southern Oscillation (ENSO) on present and past rainfall variations. This analysis has shown the stronger influence of NE trades in the location of landslide deposits in the intra-andean basin and valleys, what caused a higher contrast between summer and winter rainfall and an increasing of precipitation in La Nina years. This is believed to reduce thresholds for landslide generation in the arid to semiarid intra-andean basins and valleys. Y1 - 2000 SN - 1029-7006 ER - TY - JOUR A1 - Sitz, Andre A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Voss, Henning U. T1 - Estimation of parameters and unobserved components for nonlinear systems from noisy time series N2 - We study the problem of simultaneous estimation of parameters and unobserved states from noisy data of nonlinear time-continuous systems, including the case of additive stochastic forcing. We propose a solution by adapting the recently developed statistical method of unscented Kalman filtering to this problem. Due to its recursive and derivative-free structure, this method minimizes the cost function in a computationally efficient and robust way. It is found that parameters as well as unobserved components can be estimated with high accuracy, including confidence bands, from heavily noise-corrupted data. Y1 - 2002 UR - http://pre.aps.org/ ER - TY - JOUR A1 - Orgis, Thomas A1 - Brand, Sascha A1 - Schwarz, Udo A1 - Handorf, Dörthe A1 - Dethloff, Klaus A1 - Kurths, Jürgen T1 - Influence of interactive stratospheric chemistry on large-scale air mass exchange in a global circulation model N2 - A new globally uniform Lagrangian transport scheme for large ensembles of passive tracer particles is presented and applied to wind data from a coupled atmosphere-ocean climate model that includes interactive dynamical feedback with stratospheric chemistry. This feedback from the chemistry is found to enhance large-scale meridional air mass exchange in the northern winter stratosphere as well as intrusion of stratospheric air into the troposphere, where both effects are due to a weakened polar vortex. Y1 - 2009 UR - http://www.springerlink.com/content/1951-6355 U6 - https://doi.org/10.1140/epjst/e2009-01105-8 SN - 1951-6355 ER - TY - JOUR A1 - Schwarz, Udo A1 - Spahn, Frank A1 - Grebogi, Celso A1 - Kurths, Jürgen A1 - Petzschmann, Olaf T1 - Length scales of clustering in granular gases Y1 - 1999 ER - 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 - Krampe, Ralf-Thomas A1 - Schwarz, Udo A1 - Witt, Annette T1 - Measures of complexity in signal analysis Y1 - 1996 UR - http://agnld.uni-potsdam.de/~shw/Paper/m.ps.gz ER - TY - JOUR A1 - Kurths, Jürgen A1 - Kliem, Bernhard A1 - Schwarz, Udo A1 - Krüger, Albrecht A1 - Urpo, S. T1 - Multiresolution analysis of solar mm-wave bursts Y1 - 1998 ER - TY - JOUR A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Spahn, Frank A1 - Petzschmann, Olaf T1 - Reply on the comment of "Clustering of granular assemblies with temperature dependent restitution and under differential rotation" Y1 - 1998 ER - TY - JOUR A1 - Feudel, Ulrike A1 - Jansen, Wolfgang A1 - Kurths, Jürgen A1 - Schwarz, Udo A1 - Voss, Henning U. T1 - Solar variability : simple models and proxy data Y1 - 1997 SN - 4-274-90187-4 ER - TY - JOUR A1 - Thiel, M. A1 - Romano, Maria Carmen A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Timmer, Jens T1 - Surrogate-based hypothesis test without surrogates N2 - Fourier surrogate data are artificially generated time series, that - based on a resampling scheme - share the linear properties with an observed time series. In this paper we study a statistical surrogate hypothesis test to detect deviations from a linear Gaussian process with respect to asymmetry in time (Q-statistic). We apply this test to a Fourier representable function and obtain a representation of the asymmetry in time of the sample data, a characteristic for nonlinear processes, and the significance in terms of the Fourier coefficients. The main outcome is that we calculate the expected value of the mean and the standard deviation of the asymmetries of the surrogate data analytically and hence, no surrogates have to be generated. To illustrate the results we apply our method to the saw tooth function, the Lorenz system and to measured X-ray data of Cygnus X-1 Y1 - 2004 SN - 0218-1274 ER - TY - JOUR A1 - Wessel, Niels A1 - Schwarz, Udo A1 - Saparin, Peter A1 - Kurths, Jürgen T1 - Symbolic dynamics for medical data analysis N2 - Observational data of natural systems, as measured in medical measurements are typically quite different from those obtained in laboratories. Due to the peculiarities of these data, wellknown characteristics, such as power spectra or fractal dimension, often do not provide a suitable description. To study such data, we present here some measures of complexity, which are basing on symbolic dynamics. Firstly, a motivation for using symbolic dynamics and measures of complexity in data analysis based on the logistic map is given and next, two applications to medical data are shown. We demonstrate that symbolic dynamics is a useful tool for the risk assessment of patients after myocardial infarction as well as for the evaluation of th e architecture of human cancellous bone. Y1 - 2002 UR - http://www.agnld.uni-potsdam.de/~shw/Paper/EUROATTRACTOR2000.ps SN - 3-936142-09-2 ER - TY - JOUR A1 - Palus, Milan A1 - Kurths, Jürgen A1 - Schwarz, Udo A1 - Seehafer, Norbert A1 - Novotna, Dagmar A1 - Charvatova, Ivanka T1 - The solar activity cycle is weakly synchronized with the solar inertial motion N2 - We study possible interrelations between the 300-year record of the yearly sunspot numbers and the solar inertial motion (SIM) using the recently developed technique of synchronization analysis. Phase synchronization of the sunspot cycle and the SIM is found and statistically confirmed in three epochs (1734-1790, 1855-1875 and 1907-1960) of the whole period 1700-2000. These results give quantitative support to the hypothesis that there is a weak interaction between the solar activity and the SIM. Y1 - 2007 UR - http://www.sciencedirect.com/ science?_ob=GatewayURL&_method=citationSearch&_urlVersion=4&_origin=SDVIALERTHTML&_version=1&_uoikey=B6TVM-4MYVG5S- 1&md5=92d1fc7094be5195504f17e1afb4f0d1 U6 - https://doi.org/10.1016/j.physleta.2007.01.039 ER - TY - JOUR A1 - Cser, Adrienn A1 - Donner, Reik Volker A1 - Schwarz, Udo A1 - Otto, Andreas H. A1 - Geiger, M. A1 - Feudel, Ulrike T1 - Towards a better understanding of laser beam melt ablation using methods of statistical analysis N2 - 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. Y1 - 2002 SN - 88-87030-44-8 ER - TY - JOUR A1 - Kliem, Bernhard A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Dennis, Brian A1 - Schwartz, Richard A1 - Aschwanden, Markus J. T1 - Wavelet analysis of solar flare hard X-ray Y1 - 1998 SN - 0004-637x ER -