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1.
Cluster analysis (a Bayesian iteration procedure) was used to study the space-time distribution of sunspot groups in the time interval from 1965 to 1977. (Data were taken from the Greenwich and Debrecen Heliographic Results.) The distribution proved to be significantly non-random for the 8–10 groups cluster–1 (gr cl–1) level of clustering. Convincing evidence also favours non-random behaviour for other levels of clustering from the lowest (3–4 gr cl–1) up to the highest ( 150 gr cl–1) level. The rotation rate of the non-random pattern is generally slightly lower than the Carrington rate.The 8–10 gr cl–1 level, crudely corresponding to the sunspot nests investigated earlier, was studied in more detail. The cycle- and latitude-averaged rotational rate of the nests is slightly ( 1%) but significantly lower than the Carrington rate. Their differential rotation is strongly reduced: the cycle-averaged rotational rate varies only by 2–3% within the sunspot belt. A slight but significant bimodality is seen in the differential rotation curve: the intermediate latitudes ( 10°–20°) show a somewhat slower rotation than both the equatorial and the higher latitude regions. This might be explained by a time-dependence of the rotation rate coupled with the butterfly diagram. 相似文献
2.
K. Petrovay 《Solar physics》1991,134(2):407-410
We consider a hypothesis that nondissipating wave-bound beam structures may be created in plasma due to interaction between energetic charged particles and undamped Van Kampen (1955) waves. This hypothesis, if correct, might account for several phenomena observed in the Sun. For instance, on entering the atmosphere and then decaying, the structures may lead to flares. Furthermore, the idea offers propitious prospects of solving the well-known problem of the solar neutrino deficit. In addition, a relation between phenomena occuring within the Sun's core and those on its surface becomes possible. 相似文献
3.
R. L. Frost J. Kristof G. N. Paroz J. T. Kloprogge 《Physics and Chemistry of Minerals》1999,26(3):257-263
Upon intercalation of both ordered (low defect) and disordered (high defect) kaolinites with acetamide, two types of interaction
are observed. Firstly, hydrogen bonding between the NH2 groups of the acetamide with the siloxane oxygens is formed, as evidenced by the formation of two new bands at 3400 and 3509
cm–1. Secondly, the appearance of additional bands at ∼3600 cm–1 in both the infrared and Raman spectra of the acetamide intercalates is attributed to a second type of hydrogen bonding by
the interaction of the C=O group and the inner surface hydroxyls. Changes in the intensity of the hydroxyl deformation modes
in the 895 to 940 cm–1 region are attributed to the changes in the hydrogen bonding of the kaolinite surfaces. It is proposed that the hydrogen
bonding between the adjacent kaolinite layers is replaced with hydrogen bonding between both kaolinite surfaces and the acetamide
molecule. Changes in the molecular structure of acetamide are observed upon intercalation. The amide 1 band is lost and replaced
with a well-defined NH2 deformation vibration. The loss of the amide 1 band is attributed the hydrogen bond formation between the amide hydrogens
and the siloxane surface. The bands of the C=O group at 1680 and 1740 cm–1 become a single band at 1680 cm–1. The amide 2 band remains unchanged. The lack of intensity of the 1740 cm–1 band is attributed to the formation of hydrogen bonding between the inner surface hydroxyl groups and the carbonyl group.
Received: 4 February 1998/ Revised, accepted: 30 June 1998 相似文献
4.
Soil surface roughness (SSR) is an important factor in controlling sediment and runoff generation, influencing directly a wide spectrum of erosion parameters. SSR is highly variable in time and space under natural conditions, and characterizing SSR to improve the parameterization of hydrological and erosion models has proved challenging. Our study uses recent technological and algorithmic developments in capturing and processing close aerial sensing data to evaluate how high-resolution imagery can assist the temporally and spatially explicit monitoring of SSR. We evaluated the evolution of SSR under natural rainfall and growing vegetation conditions on two arable fields in Denmark. Unmanned aerial vehicle (UAV) photogrammetry was used to monitor small field plots over 7 months after seeding of winter wheat following conventional and reduced tillage treatments. Field campaigns were conducted at least once a month from October until April, resulting in nine time steps of data acquisition. Structure from motion photogrammetry was used to derive high-resolution point clouds with an average ground sampling distance of 2.7 mm and a mean ground control point accuracy of 1.8 mm. A comprehensive workflow was developed to process the point clouds, including the detection of vegetation and the removal of vegetation-induced point cloud noise. Rasterized and filtered point clouds were then used to determine SSR geostatistically as the standard deviation of height, applying different kernel sizes and using semivariograms. The results showed an influence of kernel size on roughness, with a value range of 0.2–1 cm of average height deviation during the monitoring period. Semivariograms showed a measurable decrease in sill variance and an increase in range over time. This research demonstrated multiple challenges to measuring SSR with UAV under natural conditions with increasing vegetation cover. The proposed workflow represents a step forward in tackling those challenges and provides a knowledge base for future research. © 2020 John Wiley & Sons, Ltd. 相似文献
5.
K. Petrovay 《Astrophysics and Space Science》1987,138(2):323-332
Some analytical relations for the phase space functions of a self-consistent spherical stellar system are derived. The integral constraints on the distribution function by imposing a given (r) density distribution andN(E) fractional energy distribution are determined. For the case of radially-anisotropic velocity distribution in theE0 limit the constraint by an exponentialN(E) implies thatf(E, J
2) tends to zero in the order (–E)3/2. This lends analytical support to the use of the Stiavelli and Bertin (1985) distribution function for modeling elliptical galaxies. Maximum phase space density constraint confirms the necessity of high collapse factors to produce such a distribution function. Limits on the steepness of an exponentialN(E) for the case when (r) resembles the emissivity law of ellipticals are also derived. 相似文献
6.
Kristof Plankensteiner Bernd M. Rode Tomas Mikoviny Armin Hansel Georg Fischer Helmut O. Rucker 《Icarus》2007,187(2):616-619
Saturn's moon Titan has been considered as one of the few places in our Solar System, where atmospheric and surface conditions could have produced organic compounds essential as precursors for an evolution of life. The Cassini-Huygens mission has provided new data on Titan's atmosphere and surface, which enabled us to simulate the chemical processes occurring under these conditions. Possible lightning events on Titan cannot only produce higher hydrocarbons, but also allow surface water ice to participate in the reaction scenario, resulting in CHO, CHN, and CHON compounds including several molecules relevant for the formation of amino acids and nucleic acids. 相似文献
7.
Anton J. J. Van Rompaey Gert Verstraeten Kristof Van Oost Gerard Govers Jean Poesen 《地球表面变化过程与地形》2001,26(11):1221-1236
In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10–5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
8.
Delineating salt-affected soils in the ganges plain by digital analysis of landsat data 总被引：1，自引：0，他引：1
A. N. Singh S. J. Kristof M. F. Baumgardner 《Journal of the Indian Society of Remote Sensing》1979,7(1):35-39
A study has been conducted to determine the feasibility of delineating salt-affected soils using computer-aided analysis of Landsat-1 data in an area of the Ganges Plain. The multispectral scanner data have been obtained on 2nd December 1972 Landsat pass. Both supervised and unsupervised classification techniques are used. Four spectral classes of salt-affected soils have been separated. The results indicate that Landsat data can be successfully used for differentiating salt-affected soils. 相似文献
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