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1.
In this paper we describe a method for separating a combination of a chaotic time series and a discrete-valued signal. The method uses a feedback technique stabilised using knowledge of the chaotic system and the discrete nature of the signal. It is not based on a linearization of the dynamics, and therefore, unlike previously proposed separation methods, does not require that the signal be small. Nor does it make any assumptions about the relative timescales of the signal and the chaotic time series. 相似文献
2.
S. T. Howard J. P. Huke I. W. Parsons S. J. Till 《International journal of quantum chemistry》1991,39(1):71-91
The usefulness of the MS -Xα method for calculating molecular transition properties is investigated in a study of NO2. Two-dimensional potential surfaces are obtained in C2v symmetry for the X?2A1/Ã2B2 system. Potential curves that approximately follow the asymmetric stretch coordinate are also presented: On investigation, no symmetry-broken solutions were found. At all nuclear geometries investigated, the muffin-tin sphere radii were chosen by an energy-minimization technique. The inclusion of corrections to the muffin-tin form of the Xα total energy is shown to be essential, if the computed surfaces are to be qualitatively correct. The transition dipole moment connecting the two states is evaluated as a function of nuclear coordinates, using the transition-state approximation. Finally, the radiative decay of a single vibronic level in NO2 is modeled and the relevance to experiment is discussed. 相似文献
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Carretero-Gonzalez R Orstavik S Huke J Broomhead DS Stark J 《Chaos (Woodbury, N.Y.)》1999,9(2):466-482
The computation of the entire Lyapunov spectrum for extended dynamical systems is a very time consuming task. If the system is in a chaotic spatio-temporal regime it is possible to approximately reconstruct the Lyapunov spectrum from the spectrum of a subsystem by a suitable rescaling in a very cost effective way. We compute the Lyapunov spectrum for the subsystem by truncating the original Jacobian without modifying the original dynamics and thus taking into account only a portion of the information of the entire system. In doing so we notice that the Lyapunov spectra for consecutive subsystem sizes are interleaved and we discuss the possible ways in which this may arise. We also present a new rescaling method, which gives a significantly better fit to the original Lyapunov spectrum. We evaluate the performance of our rescaling method by comparing it to the conventional rescaling (dividing by the relative subsystem volume) for one- and two-dimensional lattices in spatio-temporal chaotic regimes. Finally, we use the new rescaling to approximate quantities derived from the Lyapunov spectrum (largest Lyapunov exponent, Lyapunov dimension, and Kolmogorov-Sinai entropy), finding better convergence as the subsystem size is increased than with conventional rescaling. (c) 1999 American Institute of Physics. 相似文献
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Quantum mechanical ab initio simulation of the electron screening effect in metal deuteride crystals
A. Huke K. Czerski S. M. Chun A. Biller P. Heide 《The European Physical Journal A - Hadrons and Nuclei》2008,35(2):243-252
In antecedent experiments the electron screening energies of the d+d reactions in metallic environments have been determined
to be enhanced by an order of magnitude in comparison to the case of gaseous deuterium targets. The analytical models describing
averaged material properties have not been able to explain the experimental results so far. Therefore, a first effort has
been undertaken to simulate the dynamics of reacting deuterons in a metallic lattice by means of an ab initio Hartree-Fock calculation of the total electrostatic force between the lattice and the successively approaching deuterons
via path integration. The calculations have been performed for Li and Ta, clearly showing a migration of electrons from host
metallic to the deuterium atoms. However, in order to avoid more of the necessary simplifications in the model the utilization
of a massive parallel supercomputer would be required. 相似文献
7.
We report on a 3.3 μm laser/optical parametric oscillator system with 4.7 mJ pulse energy for laser ultrasound measurements of carbon-fiber-reinforced materials. The OPO was pumped by a compact diode-pumped Nd:YAG master-oscillator power-amplifier system with two amplifier stages. First results of laser ultrasound measurements are presented. 相似文献
8.
Takens Embedding Theorem forms the
basis of virtually all approaches to the analysis of time series
generated by nonlinear deterministic dynamical systems. It typically
allows us to reconstruct an unknown dynamical system which gave
rise to a given observed scalar time series simply by constructing
a new state space out of successive values of the time series.
This provides the theoretical foundation for many popular techniques,
including those for the measurement of fractal dimensions and
Liapunov exponents, for the prediction of future behaviour, for
noise reduction and signal separation, and most recently for
control and targeting. Current versions of Takens Theorem
assume that the underlying system is autonomous (and noise-free).
Unfortunately this is not the case for many real systems. In
a previous paper, one of us showed how to extend Takens
Theorem to deterministically forced systems. Here, we use similar
techniques to prove a number of delay embedding theorems for
arbitrarily and stochastically forced systems. As a special case,
we obtain embedding results for Iterated Functions Systems, and
we also briefly consider noisy observations. 相似文献
9.
N. Targosz-Ślȩczka K. Czerski A. Huke G. Ruprecht D. Weissbach L. Martin A. i. Kiliç M. Kaczmarski H. Winter 《The European physical journal. Special topics》2013,222(9):2353-2359
The enhanced electron screening effect in nuclear reactions taking place in dense astrophysical plasmas is extremely important for determination of stellar reaction rates in terrestrial laboratories as well as in prediction of cross sections enhancement in interiors of stars such as White and Brown Dwarfs or Giant Planets. This effect resulting in reduction of the nuclear Coulomb potential by the atomic electrons has been confirmed in many laboratory experiments. Unfortunately, experimental screening energies are much higher than the theoretical predictions and the reason for that remains unknown. Here, we present absorbing results of the experiment studying d + d nuclear reactions in different deuterized metallic targets under ultra high vacuum conditions. The total cross sections and angular distributions of the 2H(d,p)3H and 2H(d,n)3He reactions have been measured using a deuteron beam of energies between 8 and 30 keV provided by the electron cyclotron ion source. The atomic cleanness of the target surface has been secured by combining Ar sputtering of the target and Auger electrons spectroscopy. Due to application of an on-line analysis method, the homogeneity of the implanted deuteron densities could be continuously monitored. We will discuss probable causes of the large discrepancy between theoretical and experimental data. 相似文献
10.
N. Strauß I. Ernsting S. Schiller A. Wicht P. Huke R.-H. Rinkleff 《Applied physics. B, Lasers and optics》2007,88(1):21-28
We present a simple scheme for tuneable relative frequency stabilization of lasers. A highly sensitive and accurate frequency-to-voltage
converter is used to derive an error signal from the beat note between two lasers. We analyze in detail detector noise and
drift, modulation detection bandwidth, and cross-talk from power modulation. The results indicate that sub-kHz relative linewidth
and a locking point drift on the order of 100 Hz for times scales of 1 h are achievable. The scheme can, therefore, be applied
to situations where up to now only optical PLLs could provide sufficient accuracy and precision. To demonstrate its potential
for high-resolution, high-precision spectroscopy we lock a diode laser to a fs-frequency comb and find a relative linear drift
of 314 Hz during a 2.8 h period.
PACS 42.62.Fi; 42.62.Eh 相似文献