101,917 research outputs found
Tapping strength variability in sensorimotor experiments on rhythmic tapping
Full text linkWe report psychophysical experiments and time series analyses to investigate sensorimotor tapping strength fluctuations in human periodic tapping with and without a metronome. The power spectral density of tapping strength fluctuations typically decays in an inverse power law (1/fβ-noise) associated with long-range correlations, i.e., with a slow power-law decay of tapping strength autocorrelations and scale-free behavior. The power-law exponents β are scattered around β=1 ranging from 0.67 to 1.8. A log-linear representation of the power spectral densities reveals rhythmic peaks at frequencies f=0.25 (and f=0.5) and a tendency to slightly accentuate every fourth (and second) stroke when subjects try to synchronize their tapping with a metronome
Predicting spatio-temporal time series using dimension reduced local states
No full textWe present a method for both cross-estimation and iterated time series prediction of spatio-temporal dynamics based on local modelling and dimension reduction techniques. Assuming homogeneity of the underlying dynamics, we construct delay coordinates of local states and then further reduce their dimensionality through Principle Component Analysis. The prediction uses nearest neighbour methods in the space of dimension reduced states to either cross-estimate or iteratively predict the future of a given frame. The effectiveness of this approach is shown for (noisy) data from a (cubic) Barkley model, the Bueno-Orovio-Cherry-Fenton model, and the Kuramoto-Sivashinsky model
Estimating Lyapunov exponents in billiards
Full text linkDynamical billiards are paradigmatic examples of chaotic Hamiltonian dynamical systems with widespread applications in physics. We study how well their Lyapunov exponent, characterizing the chaotic dynamics, and its dependence on external parameters can be estimated from phase space volume arguments, with emphasis on billiards with mixed regular and chaotic phase spaces. We show that in the very diverse billiards considered here, the leading contribution to the Lyapunov exponent is inversely proportional to the chaotic phase space volume and subsequently discuss the generality of this relationship. We also extend the well established formalism by Dellago, Posch, and Hoover to calculate the Lyapunov exponents of billiards to include external magnetic fields and provide a software on its implementation
JuliaDynamics/ComplexityMeasures.jl: v2.5.0
No full textComplexityMeasures v2.5.0
Diff since v2.4.0
Closed issues:
Zenodo DOI (#221)
Merged pull requests:
move to SSSets v1 and DynamicalSystemsBase v3 (#249) (@Datseris
JuliaDynamics/ComplexityMeasures.jl: v2.7.2
No full textComplexityMeasures v2.7.2
Diff since v2.7.1
Merged pull requests:
fix binning when max point in range (#263) (@Datseris
Estimating fractal dimensions: a comparative review and open source implementations
Full text linkThe fractal dimension is a central quantity in nonlinear dynamics and can be
estimated via several different numerical techniques. In this review paper we
present a self-contained and comprehensive introduction to the fractal
dimension. We collect and present various numerical estimators and focus on the
three most promising ones: generalized entropy, correlation sum, and extreme
value theory. We then perform an extensive quantitative evaluation of these
estimators, comparing their performance and precision using different datasets
and comparing the impact of features like length, noise, embedding dimension,
falsify-ability, among many others. Our analysis shows that for synthetic
noiseless data the correlation sum is the best estimator with extreme value
theory following closely. For real experimental data we found the correlation
sum to be more strongly affected by noise versus the entropy and extreme value
theory. The recent extreme value theory estimator seems powerful as it has some
of the advantages of both alternative methods. However, using four different
ways for checking for significance, we found that the method yielded
``significant' low-dimensional results for inappropriate data like stock market
timeseries. This fact, combined with some ambiguities we found in the
literature of the method applications, have implications for both previous and
future real world applications using the extreme value theory approach, as, for
example, the argument for small effective dimensionality in the data cannot
come from the method itself. All algorithms discussed are implemented as
performant and easy to use open source code via the DynamicalSystems.jl
library
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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3346: Samuel G. Freedman, author, 2013
No full textPhotograph of author Samuel G. Freedman, at NT Daily Slash meeting in the Mayborn School of Journalism at UNT
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