排序方式: 共有2条查询结果,搜索用时 15 毫秒
1
1.
We use some fractal analysis methods to study river flow fluctuations. The result of the Multifractal Detrended Fluctuation Analysis (MF-DFA) shows that there are two crossover timescales at s1×∼12 and s2×∼130 months in the fluctuation function. We discuss how the existence of the crossover timescales are related to a sinusoidal trend. The first crossover is due to the seasonal trend and the value of second one is approximately equal to the well-known cycle of sun activity. Using Fourier Detrended Fluctuation Analysis, the sinusoidal trend is eliminated. The values of Hurst exponents of the runoff water of rivers without the sinusoidal trend show a long-range correlation behavior. For the Daugava river, the value of Hurst exponent is 0.52±0.01 and also we find that these fluctuations have multifractal nature. Comparing the MF-DFA results for the remaining data set of Daugava river to those for shuffled and surrogate series, we conclude that its multifractal nature is almost entirely due to the broadness of probability density function. 相似文献
2.
Andrejs Lusis Janis Kleperis Evalds Pentjušs 《Journal of Solid State Electrochemistry》2003,7(2):106-112
We have developed a model of electrochromic and related phenomena in tungsten oxide thin films based on the assumption that
the constitution of such films is heterogeneous and built up of nanosized particles, pores and adsorbed substances (mainly
water). It is discussed why a high-efficiency reversible blue colour is observed in amorphous tungsten oxide films (α-WO3 films) as well as why such porous thin films with polycrystalline or amorphous constitution and with a variety of particle
properties can be easily obtained by a physical vapour deposition process in a low-pressure atmosphere in the presence of
water. A substrate temperature in the range 450–550 K corresponds to some plateau on the water desorption curves which divided
physically adsorbed water from chemically adsorbed water. Two types of structural units based on tetrahedrally and octahedrally
coordinated tungsten ions have the main role in the formation of the film constitution. The tetrahedral structural units have
a glass-forming function, but the octahedral ones have a modification function. From the electrochemistry point of view, the
internal multiphase interfaces in such films are distributed multiphase electrodes. The adsorbed water together with defects
of the oxide particles provide reagents for reversible coloration reactions in the film. The colour centres can be induced
thermally (oxygen nonstoichiometry) or electrically (injected ions) or by radiation (photoinjected hydrogen). The electrochromism
and related phenomenon of α-WO3 films can be directly related to ion insertion/extraction processes controlled by external forces.
Electronic Publication 相似文献
1