共查询到20条相似文献,搜索用时 31 毫秒
1.
《New Astronomy》2003,8(2):105-117
Wavelet analysis of different solar activity indices—sunspot numbers, sunspot areas and flare index—allows us to investigate the time evolution of some frequency dependent functionals, like wavelet entropy, which gives useful information about the complexity level of the related signals. The main aim of this work is the analysis of the time behavior of wavelet entropy near the maximum phases of solar cycles 21–22–23 in order to further contribute to the characterization of the multi-peaked structure of solar cycle maxima and to support the current interpretation of the so-called Gnevyshev gap. 相似文献
2.
H.J. Haubold 《Astrophysics and Space Science》1997,258(1-2):201-218
Wavelet analysis offers an alternative to Fourier based time- series analysis and is particularly useful when spectral features
are time dependent. We analyze the solar neutrino capture rate of the radiochemical Homestake chlorine experiment with abbreviated
Morlet wavelets, using Foster's (AJ, 111,1709(1996)) rescaled wavelet technique. We emphasize the complementarity of wavelet
analysis to Fourier analysis. Wavelet analysis confirms the results of previously undertaken Fourier analysis. The Homestake
data seem to contain a harmonic content with periodicities of 4.76 yr, 1.89 yr, 0.85 yr, and 0.51 yr. Wavelet analysis reveals
that the 4.76 yr and 1.89 yr periods show an almost constant behavior over the 25 yr Homestake data record, while the 0.85
yr and 0.51 yr periods exhibit a transient phenomenon. The analysis does not show strong evidence for a period of the solar
11 yr cycle.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Dmitri I. Ponyavin 《Solar physics》2004,224(1-2):465-471
Historical geomagnetic and climate records were analyzed to study long-term trends and relationships with solar activity.
Wavelet technique and recurrence plot analysis are applied to the data to find their coherence and similarities at different
times and time-scales. It is shown that the solar cycle signal is more pronounced in climatic data during the last 60 years. 相似文献
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Elena Aleksandrovna Bruevich Vasily Vladimirovich Bruevich Boris Pavlovich Artamonov 《天文和天体物理学研究(英文版)》2018,(7)
The wavelet transform method for high-quality time-frequency analysis is applied to sets of observations of relative sunspot numbers and stellar chromosphere fluxes of 10 Sun-like stars.Wavelet analysis of solar data shows that in a certain interval of time there are several cycles of activity with periods of duration which vary considerably from each other:from quasi-biennial cycles to 100-yr cycles.Cyclic activity was detected in almost all Sun-like stars that we examined,even those that previously were not considered as stars with cyclic activity according to analysis using a Scargle periodogram.The durations of solar and stellar cycles significantly change during the observation period. 相似文献
7.
Pablo M. Cincotta † 《Monthly notices of the Royal Astronomical Society》1999,307(4):941-948
In two recent papers a new method for searching for periodicity in time series was introduced. It takes advantage of the Shannon entropy to compute the amount of information contained in the light curve of a given signal as a function of a supposed period p . The basic result is that, if the signal is T -periodic, the entropy is then minimum when p T . Also, there is theoretical and numerical evidence that the minimum entropy method is more sensitive to the presence of periodicity and has a higher resolution power than other classical techniques. In the present work the discussion is focused on the way in which the observational errors have to be included in the method. The application of the resulting modified algorithm to real data and a performance comparison with the former algorithm are presented. The dependence of both periodograms on the size of the partition is also investigated. Analytical estimates are given only for the limiting case of small errors. The numerical results show that the new algorithm leads to a smoother periodogram and provides a higher significance for the minimum than the former algorithm. 相似文献
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Using Unruh-Verlinde temperature obtained by entropic force, we directly calculate partition functions of quantum field in Schwarzschild spacetime via quantum statistical method and derive the expression of the black hole statistical entropy. In our calculation the lower limit of integral is the location of isolated horizon introduced in loop quantum gravity and the upper limit of integral is infinity. So the obtained entropy is the statistical entropy from isolated horizon to the infinite. In our calculation there are not the cutoff and approximation. The results showed that, as long as proper Immirzi parameters are selected, the entropy obtained by loop quantum gravity is consistent with the quantum statistical entropy outside the black hole horizon. Therefore the black hole entropy is a quantum entanglement entropy outside the isolated horizon. 相似文献
10.
With the increasing of applications of Global Positioning System (GPS), the research on the factors affecting the radio signals is becoming more and more important. One of the most significant effects on ionosphere monitoring is the ionospheric radio occultation (IRO), and the IRO data is now serving as one of the most important monitoring sources for the ionospheric measurements. Meanwhile the inversion of the occultation data is a popular topic. The traditional Abel inversion process through compensated total electron content (TEC) is a linear inversion method, thus it would transfer the measurement errors directly to the inversion results. In order to improve the occultation results, we introduce in this paper two nonlinear methods, namely the regularization method and the maximum entropy regularization method. Through designed simulative experiments, we verify and compare these three methods, and conclude that the maximum entropy regularization method can reduce significantly the influence of measurement errors. 相似文献
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Biman B. Nath 《Journal of Astrophysics and Astronomy》2011,32(4):545-548
The Intracluster Medium (ICM) is believed to have been affected by feedback from Active Galactic Nuclei (AGN) and/or supernovae-driven
winds. These sources are supposed to have injected entropy into the ICM gas. The recently determined universal pressure profile
of the ICM gas has been used and after comparing with the entropy profile of the gas from gravitational effects of the dark
matter halo, the additional entropy injected by non-gravitational sources, as a function of the total cluster mass is determined.
The current observational data of red-shift evolution of cluster scaling relation is shown that allow models in which the
entropy injection decreases at high red-shift. 相似文献
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Using the quantum statistical method, we calculate quantum statistical entropy between the black hole horizon and the cosmological horizon in Schwarzchild spacetime and derive the expression of quantum statistical entropy in de Sitter spacetime. Under the Unruh-Verlinde temperature of Schwarzchild-de Sitter spacetime in the entropic force views, we obtain the expression of quantum statistical entropy in de Sitter spacetime. It is shown that in de Sitter spacetime quantum statistical entropy is the sum of thermodynamic entropy corresponding black hole horizon and the one corresponding cosmological horizon. And the correction term of de Sitter spacetime entropy is obtained. Therefore, it is confirmed that the black hole entropy is the entropy of quantum field outside the black hole horizon. The entropy of de Sitter spacetime is the entropy of quantum field between the black hole horizon and the cosmological horizon. 相似文献
15.
T. Ibungochouba Singh I. Ablu Meitei K. Yugindro Singh 《Astrophysics and Space Science》2013,345(1):177-181
Hawking radiation of Kerr-de Sitter black hole is investigated using Hamilton-Jacobi method. When the well-behaved Painleve coordinate system and Eddington coordinate are used, we get the correct result of Bekenstein-Hawking entropy before and after radiation but a direct computation will lead to a wrong result via Hamilton-Jacobi method. Our results show that the tunneling probability is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal but it is consistent with underlying unitary theory. 相似文献
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To predict the key parameters of the solar cycle,a new method is proposed based on the empirical law describing the correlation between the maximum height of the preceding solar cycle and the entropy of the forthcoming one.The entropy of the forthcoming cycle may be estimated using this empirical law,if the maximum height of the current cycle is known.The cycle entropy is shown to correlate well with the cycle's maximum height and,as a consequence,the height of the forthcoming maximum can be estimated.In turn,the correlation found between the height of the maximum and the duration of the ascending branch(the Waldmeier rule)allows the epoch of the maximum,Tmax,to be estimated,if the date of the minimum is known.Moreover,using the law discovered,one can find out the analogous cycles which are similar to the cycle being forecasted,and hence,obtain the synoptic forecast of all main features of the forthcoming cycle.The estimates have shown the accuracy level of this technique to be 86%.The new regularities discovered are also interesting because they are fundamental in the theory of solar cycles and may provide new empirical data.The main parameters of the future solar cycle 24 are as follows: the height of the maximum is Wmax = 95±20,the duration of the ascending branch is Ta = 4.5±0.5 yr,the total cycle duration according to the synoptic forecast is 11.3 yr. 相似文献
18.
Robert W. Johnson 《Astrophysics and Space Science》2012,338(1):35-48
The principle of maximum entropy is applied to the spectral analysis of a data signal with general variance matrix and containing
gaps in the record. The role of the entropic regularizer is to prevent one from overestimating structure in the spectrum when
faced with imperfect data. Several arguments are presented suggesting that the arbitrary prefactor should not be introduced
to the entropy term. The introduction of that factor is not required when a continuous Poisson distribution is used for the
amplitude coefficients. We compare the formalism for when the variance of the data is known explicitly to that for when the
variance is known only to lie in some finite range. The result of including the entropic measure factor is to suggest a spectrum
consistent with the variance of the data which has less structure than that given by the forward transform. An application
of the methodology to example data is demonstrated. 相似文献
19.
由于差错控制在超宽带室内导航系统中占据着十分重要的位置,并考虑到IEEE802.15.3a标准采用卷积编码和Viterbi译码来进行差错控制,因此利用现场可编程门阵列(FPGA)设计实现了一种约束长度为7,译码深度为64的全并行Viterbi译码器。本设计在xilinx ISE9.2环境下进行了综合,并采用Modelsim6.0对整个设计进行了仿真。仿真结果表明,该设计能够满足超宽带系统的要求。 相似文献
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In this paper, the generalized second law (GSL) of thermodynamics and entropy is revisited in the context of cosmological
models in Gauss-Bonnet gravity with the boundary of the universe is assumed to be enclosed by the dynamical apparent horizon.
The model is best fitted with the observational data for distance modulus. The best fitted geometric and thermodynamic parameters
such as equation of state parameter, deceleration parameter and entropy are derived. To link between thermodynamic and geometric
parameters, the “entropy rate of change multiplied by the temperature” as a model independent thermodynamic state parameter
is also derived. The results show that the model is in good agreement with the observational analysis. 相似文献