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991.
I. S. Veselovsky A. V. Dmitriev A. V. Suvorova M. V. Tarsina 《Journal of Astrophysics and Astronomy》2000,21(3-4):423-429
The cyclic evolution of the heliospheric plasma parameters is related to the time-dependent boundary conditions in the solar
corona. “Minimal” coronal configurations correspond to the regular appearance of the tenuous, but hot
and fast plasma streams from the large polar coronal holes. The denser, but cooler and slower solar wind is adjacent to coronal
streamers. Irregular dynamic manifestations are present in the corona and the solar wind everywhere and always. They follow
the solar activity cycle rather well. Because of this, the direct and indirect solar wind measurements demonstrate clear variations
in space and time according to the minimal, intermediate and maximal conditions of the cycles. The average solar wind density,
velocity and temperature measured at the Earth’s orbit show specific decadal variations and trends, which are of
the order of the first tens per cent during the last three solar cycles. Statistical, spectral and correlation characteristics
of the solar wind are reviewed with the emphasis on the cycles. 相似文献
992.
The observed density of Venus is about 2% smaller than would be expected if Venus were a twin planet of the Earth, possessing an identical internal composition and structure. In principle, this could be explained by a process of physical segregation of metal particles from silicate particles in the solar nebula prior to accretion, so that Venus accreted from relatively metal-depleted material. However, this model encounters severe difficulties in explaining the nature of the physical segregation process and also the detailed chemical composition of the Earth's mantle. Two alternative hypotheses are examined, both of which attempt to explain the density difference in terms of chemical fractionation processes. Both of these hypotheses assume that the relative abundances of the major elements Fe, Si, Mg, Al, and Ca are similar in both planets. According to the first hypothesis, a larger proportion of the total iron in Venus is present as iron oxide in the mantle, so that the core-to-mantle ratio is smaller than in the Earth. This model implies that Venus is more oxidized than the Earth, with its lower intrinsic density (i.e., corrected to equivalent pressures and temperatures) due to the larger amount of oxygen present. The difference between oxidation states is attributed to differing degrees of accretional heating arising from the relatively smaller mass of Venus. On the other hand, the second hypothesis maintains that Venus is more reduced than the Earth, with its mantle essentially devoid of oxidized iron. The difference intrinsic densities is attributed to the Earth accreting at a lower temperature than Venus as a result of the Earth's greater distance from the center of the nebula. As a result, large amounts of sulfur accreted on the Earth but not on Venus. The sulfur, which entered the core, is believed to have increased the mean density of the Earth because of its relatively high atomic weight. The hypothesis also implies that most of the Earth's potassium, because of its chalcophile properties, entered the core.These hypotheses are evaluated in the light of existing data. The second hypothesis leads to an intrinsic density for Venus which is only 0.4% smaller than that of the Earth. This difference is much smaller than is believed to exist. A wide range of chemical evidence is found to be unfavorable to this second hypothesis, but to be consistent with the interpretation that Venus is more oxidized than the Earth, as required by the first hypothesis. 相似文献
993.
The eSTAR Project uses intelligent agent technologies to carry out resource discovery, submit observation requests and analyze the reduced data returned from a meta‐network of robotic telescopes. Linking ground based telescopes with astronomical satellites, and using the emerging field of intelligent agent architectures to provide crucial autonomous decision making in software, the project has succeeded in combining data archives and research class telescopes, along with distributed computing nodes, to build an ad‐hoc peer‐to‐peer heterogeneous network of resources. We present the current operations paradigm of the eSTAR network and describe the direction in which the project intends to develop over the next few years. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
E.K. Hege E.N. Hubbard J.D. Drummond P.A. Strittmatter S.P. Worden T. Lauer 《Icarus》1982,50(1):72-81
We report speckle interferometric observations of Pluto and its moon (1978 P1) Charon obtained on 5 June 1980 with a single 1.8-m mirror of the Multiple Mirror Telescope. Our observations yield a separation of 0″.31 (±0″.05) between Pluto and Charon at position angle 285° (±7°) for JD 2444395.75. This result and other direct observations indicate an adjustment of +4.0 hr to the orbital epoch of R. S. Harrington and J. W. Christy [Astron.J.86, 442–443 (1981)]. Our observation, which represents the first resolution of the system near minimum separation, also suggests that the inclination of the orbit to the plane of the sky should be increased by 3°; this will delay the onset of the predicted eclipsee season by one apparition to 1984 or 1985. Our data are consistent with Pluto diameter 0″.14 (±0″.02) = 3000 (±400) km and Charon diameter 0″..05 (±0″.03) = 1100 (±600) km. 相似文献
995.
A. Farmany 《Astrophysics and Space Science》2012,338(2):401-403
The derivation of the thermodynamics uncertainty to anti de Sitter space-time is carried out. The entropy of anti de Sitter
space is obtained. Furthermore, for first time, the electromagnetic signal related to the Hawking radiation is suggested to
be calculated which may be a key factor in realizing black holes in both cosmos and lab. 相似文献
996.
M. M. Pevzner M. L. Tolstykh A. D. Babansky 《Journal of Volcanology and Seismology》2018,12(4):242-251
It is shown that Shiveluch, which consists of several volcanic edifices that stand in one area and in part overlie each other, is a long-lived volcanic massif with a complex structure. The available data on the morphology of the edifice, age, rock compositions, primary melts, and types of eruptive activity were used to identify structurally-temporal units (STUs) in the Shiveluch volcanic massif. It was found that the generation of different-age STUs was due to the activity of at least four magma chambers with different parameters. The durations of the individual chambers were determined. The activities of these chambers were initiated and came to an end nearly instantaneously because of major collapse episodes in the edifice of the massif due to high-magnitude earthquakes. 相似文献
997.
Synchronization trends and rhythms of multifractal parameters of the field of low-frequency microseisms 总被引:2,自引:0,他引:2
A. A. Lyubushin 《Izvestiya Physics of the Solid Earth》2009,45(5):381-394
The field of low-frequency microseisms is investigated with the use of data from 83 stations of the F-net broadband network in Japan over the period from the beginning of 1997 through June 2008. Vertical components with a sampling step of 1 s are used for analysis, as well as signals with a sampling step of 1 min obtained from the initial data by averaging and thinning. Long-period regularities of changes in the singularity spectrum support width Δα and the generalized Hurst exponent α* for the field of low-frequency microseisms were revealed by estimating multifractal singularity spectra in consecutive time windows 30 min long for 1-s data and 24 hour long for 1-min data. The average value of the parameter α* for 1-s data significantly decreased before the Hokkaido earthquake of September 25, 2003 (M = 8.3), and was not restored subsequently to its previous level. Prior to September 2003, 1-min data on α* variations experienced strong annual changes, which completely ceased afterwards. Both these effects are interpreted as an increase in the degree of synchronization of microseismic noise on Japan’s islands after the September 25, 2003, earthquake. This hypothesis is also supported by estimates of the measures of correlation and spectral coherence between variations in the average values of Δα and α* calculated for 1-min data inside five spatial clusters of stations from consecutive time fragments two months long. Based on the well-known statement of the theory of catastrophes that synchronization is one of the flags of an approaching catastrophe, it was suggested that the Hokkaido event could be a foreshock of an even stronger earthquake nucleating in the region of Japan’s islands. 相似文献
998.
999.
1000.
A. A. Azimi T. Navab Daneshmand M.Sc. A. Pardakhti M.Sc. 《International Journal of Environmental Science and Technology》2006,3(2):177-180
This study is done to measure the absorption and distribution of cadmium in different parts of kidney beans, radishes and pumpkins. Three parts of a field was chosen. In one part 65 ppm of cadmium nitrate was added to water and in the other part 130 ppm, the last part was irrigated with normal water. Samples were digested by EPA 3050 method. Cadmium concentration was measured by Unicam 919 absorption unit. Beans accumulate cadmium mostly in root (70 ppm) and a little amount is mobilized through upper parts (12–16ppm), but kidneys did not accumulate a significant amount. In radishes the roots did not accumulate a significant amount of cadmium but stems had 4 ppm and leaves had 25 ppm. Cadmium concentration in soil does not affect its concentration in different parts of pumpkins and beside the stems and leaves (4 ppm) the other parts' concentrations were insignificant. In regard to the results of this study the cadmium concentrations in edible parts of the samples (kidney beans, radish roots and pumpkin fruit) were less than the U.S. EPA standards for agriculture and human beings. 相似文献