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11.
This paper reports the results of a study of the N-S asymmetry in the flare index using the results of Knoka (1985) combined with our results for the solar cycles 17 to the current cycle 22. By comparing the time-variation of the asymmetry curve with the solar activity variation of the 11-year cycle, we have found that the flare index asymmetry curve is not in phase with the solar cycle and that the asymmetry peaks during solar minimum. A periodic behaviour in the N-S asymmetry appears: the activity in one hemisphere is more important during the ascending part of the cycle whereas during the descending part the activity becomes more important in the other hemisphere. The dominance of flare activity in the southern hemisphere continues during cycle 22 and, according to our findings, this dominance will increase gradually during the following cycle 23. 相似文献
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The short-term periodicities of the flare index are investigated in detail using Fourier and wavelet transforms for the full disc and for the northern and the southern hemispheres of the Sun separately over the epoch of almost 4 cycles (1966–2002). The most pronounced power peaks were found by the Fourier transform to be present at 25.6, 27.0, 30.2, and 33.8 days. The wavelet transform results show that the occurrence of periodicities of flare index power is highly intermittent in time. A comparison of the results of the Fourier transform and the time-period wavelet transform of the flare index time series has clarified the importance of different periodicities, whether they are or are not the harmonics of the basic ones, as well as the temporal location of their occurrence. We found that the modulation of the flare index due to the 27-day solar rotation is more pronounced during the declining portion of solar cycle than during the rising portion. 相似文献
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Oil decolorization properties of the Emirler clinoptilolite and its acid-activated forms were studied using neutralized cottonseed oil. Although the oil decolorization capacity of natural clinoptilolite is low, it can be improved by a factor of 1.8 after HCl activation under the optimized conditions (1M HCl, solid/liquid ratio = 1/20, T = 25°C, t = 1 hour). Acid activation increases the total specific surface area from 40 to 70 m2/g which is mostly realized with a pore diameter range smaller than 15 nm. The bleaching capacity of acid-activated clinoptilolite is comparable to that of natural bentonitic clays but it is 1.6 times lower than the capacity of activated bleaching earths such as Tonsil and others. However, the amount of oil absorbed by clinoptilolite during the bleaching process is almost half that compared with the commonly used natural and acid-activated clays. 相似文献
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Modelling time series of groundwater levels is investigated by three fuzzy logic (FL) models, Sugeno (SFL), Mamdani (MFL) and Larsen (LFL), using data from observation wells. One novelty in the study is the re-use of these three models as multiple models through the following strategies: (a) simple averaging, (b) weighted averaging and (c) committee machine techniques; these are implemented using artificial neural networks (ANN). These strategies provide some evidence that (i) multiple models improve on the performance of individual models and those using committee machines perform better than the other two options; and (ii) committee machine models produce defensible modelling results to develop management scenarios. The study investigates water table declines through management scenarios and shows that in this aquifer water use has higher impacts on water table variations than climatic variations. This provides evidence of the need for planned management in the study area. 相似文献
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Andrés E. Piatti João F. C. SantosJr Juan J. Clariá Eduardo Bica Ata Sarajedini Doug Geisler 《Monthly notices of the Royal Astronomical Society》2001,325(2):792-802
Colour–magnitude diagrams are presented for the first time for L32, L38, K28 (L43), K44 (L68) and L116, which are clusters projected on to the outer parts of the Small Magellanic Cloud (SMC). The photometry was carried out in the Washington system C and T 1 filters, allowing the determination of ages by means of the magnitude difference between the red giant clump and the main-sequence turn-off, and metallicities from the red giant branch locus. The clusters have ages in the range 2–6 Gyr , and metallicities in the range −1.65<[Fe/H]<−1.10, increasing the sample of intermediate-age clusters in the SMC. L116, the outermost cluster projected on to the SMC, is a foreground cluster, and somewhat closer to us than the Large Magellanic Cloud. Our results, combined with those for other clusters in the literature, show epochs of sudden chemical enrichment in the age–metallicity plane, which favour a bursting star formation history as opposed to a continuous one for the SMC. 相似文献