53,090 research outputs found
Bivariate phase-rectified signal averaging
Phase-Rectified Signal Averaging (PRSA) was shown to be a powerful tool for
the study of quasi-periodic oscillations and nonlinear effects in
non-stationary signals. Here we present a bivariate PRSA technique for the
study of the inter-relationship between two simultaneous data recordings. Its
performance is compared with traditional cross-correlation analysis, which,
however, does not work well for non-stationary data and cannot distinguish the
coupling directions in complex nonlinear situations. We show that bivariate
PRSA allows the analysis of events in one signal at times where the other
signal is in a certain phase or state; it is stable in the presence of noise
and impassible to non-stationarities.Comment: 19 pages, 6 figures, revised version submitted to Physica
New mechanism for non-trivial intra-molecular vibrational dynamics
We investigate the time evolution process of one selected (initially prepared
by optical pumping) vibrational molecular state, coupled to all other
intra-molecular vibrational states of the same molecule, and also to its
environment. Molecular states forming the first reservoir are characterised by
a discrete dense spectrum, whereas the environment reservoir states form a
continuous spectrum. Assuming the equidistant reservoir states we find the
exact analytical solution of the quantum dynamic equations. System reservoirs
couplings yield to spontaneous decay of the states, whereas system-reservoir
exchange leads to recurrence cycles and Loschmidt echo and double resonances at
the interlevel reservoir transitions. Due to these couplings the system
time evolution is not reduced to a simple exponential relaxation. We predict
various regimes of the system dynamics, ranging from exponential decay to
irregular damped oscillations. Namely, we show that there are four possible
dynamic regimes of the evolution: (i) - independent of the environment
exponential decay suppressing backward transitions, (ii) Loschmidt echo regime,
(iii) - incoherent dynamics with multicomponent Loschmidt echo, when the system
state exchanges its energy with many states of the reservoir, (iv) - cycle
mixing regime, when the long term system dynamics appear to be random. We
suggest applications of our results for interpretation of femtosecond vibration
spectra of large molecules and nano-systems.Comment: 11 pages, 2 figure
Classification of EMI discharge sources using timeâfrequency features and multi-class support vector machine
This paper introduces the first application of feature extraction and machine learning to Electromagnetic Interference (EMI) signals for discharge sources classification in high voltage power generating plants. This work presents an investigation on signals that represent different discharge sources, which are measured using EMI techniques from operating electrical machines within power plant. The analysis involves Time-Frequency image calculation of EMI signals using General Linear Chirplet Analysis (GLCT) which reveals both time and frequency varying characteristics. Histograms of uniform Local Binary Patterns (LBP) are implemented as a feature reduction and extraction technique for the classification of discharge sources using Multi-Class Support Vector Machine (MCSVM). The novelty that this paper introduces is the combination of GLCT and LBP applications to develop a new feature extraction algorithm applied to EMI signals classification. The proposed algorithm is demonstrated to be successful with excellent classification accuracy being achieved. For the first time, this work transfers expert's knowledge on EMI faults to an intelligent system which could potentially be exploited to develop an automatic condition monitoring system
Statistical Theory for Incoherent Light Propagation in Nonlinear Media
A novel statistical approach based on the Wigner transform is proposed for
the description of partially incoherent optical wave dynamics in nonlinear
media. An evolution equation for the Wigner transform is derived from a
nonlinear Schrodinger equation with arbitrary nonlinearity. It is shown that
random phase fluctuations of an incoherent plane wave lead to a Landau-like
damping effect, which can stabilize the modulational instability. In the limit
of the geometrical optics approximation, incoherent, localized, and stationary
wave-fields are shown to exist for a wide class of nonlinear media.Comment: 4 pages, REVTeX4. Submitted to Physical Review E. Revised manuscrip
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