36,107 research outputs found
A new look at low-energy nuclear reaction (LENR) research: a response to Shanahan
In his criticisms of the review article on LENR by Krivit and Marwan, Shanahan has raised a number of issues in the areas of calorimetry, heat after death, elemental transmutation, energetic particle detection using CR-39, and the temporal correlation between heat and helium-4. These issues are addressed by the researchers who conducted the original work that was discussed in the Krivit-Marwan (K&M) review paper
How to avoid potential pitfalls in recurrence plot based data analysis
Recurrence plots and recurrence quantification analysis have become popular
in the last two decades. Recurrence based methods have on the one hand a deep
foundation in the theory of dynamical systems and are on the other hand
powerful tools for the investigation of a variety of problems. The increasing
interest encompasses the growing risk of misuse and uncritical application of
these methods. Therefore, we point out potential problems and pitfalls related
to different aspects of the application of recurrence plots and recurrence
quantification analysis
Quantifying Changes in the Spatial Structure of Trabecular Bone
We apply recently introduced measures of complexity for the structural
quantfication of distal tibial bone. For the first time, we are able to
investigate the temporal structural alteration of trabecular bone. Based on
four patients, we show how bone may alter due to temporal immobilisation
Recurrence Plots 25 years later -- gaining confidence in dynamical transitions
Recurrence plot based time series analysis is widely used to study changes
and transitions in the dynamics of a system or temporal deviations from its
overall dynamical regime. However, most studies do not discuss the significance
of the detected variations in the recurrence quantification measures. In this
letter we propose a novel method to add a confidence measure to the recurrence
quantification analysis. We show how this approach can be used to study
significant changes in dynamical systems due to a change in control parameters,
chaos-order as well as chaos-chaos transitions. Finally we study and discuss
climate transitions by analysing a marine proxy record for past sea surface
temperature. This paper is dedicated to the 25th anniversary of the
introduction of recurrence plots
Cross-Recurrence Quantification Analysis of Categorical and Continuous Time Series: an R package
This paper describes the R package crqa to perform cross-recurrence
quantification analysis of two time series of either a categorical or
continuous nature. Streams of behavioral information, from eye movements to
linguistic elements, unfold over time. When two people interact, such as in
conversation, they often adapt to each other, leading these behavioral levels
to exhibit recurrent states. In dialogue, for example, interlocutors adapt to
each other by exchanging interactive cues: smiles, nods, gestures, choice of
words, and so on. In order for us to capture closely the goings-on of dynamic
interaction, and uncover the extent of coupling between two individuals, we
need to quantify how much recurrence is taking place at these levels. Methods
available in crqa would allow researchers in cognitive science to pose such
questions as how much are two people recurrent at some level of analysis, what
is the characteristic lag time for one person to maximally match another, or
whether one person is leading another. First, we set the theoretical ground to
understand the difference between 'correlation' and 'co-visitation' when
comparing two time series, using an aggregative or cross-recurrence approach.
Then, we describe more formally the principles of cross-recurrence, and show
with the current package how to carry out analyses applying them. We end the
paper by comparing computational efficiency, and results' consistency, of crqa
R package, with the benchmark MATLAB toolbox crptoolbox. We show perfect
comparability between the two libraries on both levels
Secular variation of hemispheric phase differences in the solar cycle
We investigate the phase difference of the sunspot cycles in the two
hemispheres and compare it with the latitudinal sunspot distribution. If the
north-south phase difference exhibits a long-term tendency, it should not be
regarded as a stochastic phenomenon.
We use datasets of historical sunspot records and drawings made by
Staudacher, Hamilton, Gimingham, Carrington, Spouml;rer, and Greenwich
observers, as well as the sunspot activity during the Maunder minimum
reconstructed by Ribes and Nesme-Ribes.
We employ cross-recurrence plots to analyse north-south phase differences. We
show that during the last 300 years, the persistence of phase-leading in one of
the hemispheres exhibits a secular variation. Changes from one hemisphere to
the other leading in phase were registered near 1928 and 1968 as well as two
historical ones near 1783 and 1875.
A long-term anticorrelation between the hemispheric phase differences in the
sunspot cycles and the latitudinal distribution of sunspots was traced since
1750.Comment: 7 pages, 4 figure
Recurrence-based time series analysis by means of complex network methods
Complex networks are an important paradigm of modern complex systems sciences
which allows quantitatively assessing the structural properties of systems
composed of different interacting entities. During the last years, intensive
efforts have been spent on applying network-based concepts also for the
analysis of dynamically relevant higher-order statistical properties of time
series. Notably, many corresponding approaches are closely related with the
concept of recurrence in phase space. In this paper, we review recent
methodological advances in time series analysis based on complex networks, with
a special emphasis on methods founded on recurrence plots. The potentials and
limitations of the individual methods are discussed and illustrated for
paradigmatic examples of dynamical systems as well as for real-world time
series. Complex network measures are shown to provide information about
structural features of dynamical systems that are complementary to those
characterized by other methods of time series analysis and, hence,
substantially enrich the knowledge gathered from other existing (linear as well
as nonlinear) approaches.Comment: To be published in International Journal of Bifurcation and Chaos
(2011
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