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991.
The structure of the averaged plasma pressure distribution in the plasma ring around the Earth at geocentric distances of
∼6–10R
E
has been determined. The distribution function moments measured on the international THEMIS mission satellites have been
used. The plasma pressure distribution in the equatorial plane at 15R
E
> XSM > −15R
E
and 15R
E
> YSM > −15R
E
has been statistically studied. The radial dependence of the plasma pressure at the day-night and morning-evening meridians
has been analyzed. It has been indicated that the plasma ring around the Earth has a structure, which is close to being azimuthally
symmetric. The achieved results have been compared with the pressure distributions obtained previously. It has been indicated
that in the overlapping regions, the achieved results agree with the previously obtained data within the pressure determination
errors. 相似文献
992.
Modern methods of analyses of environment yield multivariate data sets of measured objects which are used as the basis of the evaluation and interpretation of substances, differentiated effects, but also of samples or processes. The integrated evaluation and assessment of such multivariate data requires the application of mathematical-statistical methods, the method of pattern recognition being particularly suitable. Pattern recognition program systems constitute a compilation of different methods, as e.g. the multivariate linear regression, classification methods (discriminant analysis, multivariate variance analysis), cluster algorithms, multidimensional scaling, factorial analysis. A few possibilities of such pattern comparisons and identifications are represented by the example of gas chromatography and of the structure/effect analysis for the mutagenity to be expected of 117 substances. 相似文献
993.
Patrick F. Cummins Gary S.E. Lagerloef 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):365
Interannual variability of the sea surface height (SSH) over the northeast Pacific Ocean is hindcast with a reduced-gravity, quasi-geostrophic model that includes linear damping. The model is forced with monthly Ekman pumping fields derived from the NCEP reanalysis wind stresses. The numerical solution is compared with SSH observations derived from satellite altimeter data and gridded at a lateral resolution of 1 degree. Provided that the reduced gravity parameter is chosen appropriately, the results demonstrate that the model has significant hindcast skill over interior regions of the basin, away from continental boundaries. A damping time scale of 2 to 3 years is close to optimal, although the hindcast skill is not strongly dependent on this parameter.A simplification of the quasi-geostrophic model is considered in which Rossby waves are eliminated, yielding a Markov model driven by local Ekman pumping. The results approximately reproduce the hindcast skill of the more complete quasi-geostrophic model and indicate that the interannual SSH variability is dominated by the local response to wind forcing. There is a close correspondence the two leading empirical orthogonal modes of the local model and those of the observed SSH anomalies. The latter account for over half of the variance of the interannual signal over the region. 相似文献
994.
Preston E. James 《The Professional geographer》1976,28(1):1-7
Every active scientific discipline has arrived at its own peculiar definition of acceptable problems and acceptable ways of attacking them through a social process of mutual consent. 相似文献
995.
The way of extraction of insoluble carbonaceous substance (ICS) from black shales and technique of determination of noble metals (NM) in it by direct arc atomic emission analysis (AEA) were developed. The first results are reported on the determination of mineral-bound noble metals in ICS concentrates, which were extracted from the rocks and ores of the Sukhoi Log, Vernyi, Vasil’evskoe, Kuranakh, Daugyztau, Bakyrchik, Kamennoe, El’dorado, and other deposits. 相似文献
996.
997.
998.
Understanding the natural spatial and temporal variability that exists within an ecosystem is a critical component of efforts
to restore systems to their natural state. Analysis of benthic foraminifers and molluscs from modern monitoring sites within
Florida Bay allows us to determine what environmental parameters control spatial and temporal variability of their assemblages.
Faunal assemblages associated with specific environmental parameters, including salinity and substrate, serve as proxies for
an interpretation of paleoecologic data. The faunal record preserved in two shallow (<2 m) cores in central Florida Bay (Russell
Bank and Bob Allen Bank) provides a record of historical trends in environmental parameters for those sites. Analysis of these
two cores has revealed two distinct patterns of salinity change at these sites: 1) a long-term trend of slightly increasing
average salinity; and 2) a relatively rapid change to salinity fluctuations of greater frequency and amplitude, beginning
around the turn of the century and becoming most pronounced after 1940. The degree of variability in substrate types at each
locality limits interpretations of substrate trends to specific sites. A common sequence of change is present in the Russell
Bank and Bob Allen Bank cores: from mixed grass and bare-sediment indicators at the bottom of the cores, to bare-sediment
dwellers in the center, to a dominance of vegetative-cover indicators at the top of the cores. Changes in interpreted salinity
patterns around the turn of the century are consistent with the timing of the construction of the Flagler Railroad from 1905
to 1912, and the Tamiami Trail and the canal and levee systems between 1915 and 1928. Beginning around 1940, the changes in
the frequency and amplitude of salinity fluctuations may be related to changes in water management practices, meteorologic
events (frequent hurricanes coupled with severe droughts in 1943 and 1944), or a combination of factors. The correspondence
of these changes in Florida Bay with changes in the terrestrial Everglades suggests factors affecting the entire ecosystem
are responsible for the salinity and substrate patterns seen in Florida Bay. 相似文献
999.
J. F. Read M. I. Lucas S. E. Holley R. T. Pollard 《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(12):2341-2367
A survey was made of the Southwest Indian Ocean frontal region between 30 and 50°E containing the Agulhas Return, Subtropical and Subantarctic Fronts. From CTD, SeaSoar and extracted samples the distribution of nitrate, silicate and chlorophyll a is shown to be strongly linked to the front and water mass structure, varying zonally and meridionally. Surface chlorophyll a concentrations were low to the north and south leaving a band of elevated chlorophyll between the Subtropical and Subantarctic Fronts. The low concentration of chlorophyll a to the north, in Subtropical Water, was clearly due to nitrate limitation. Between the Subtropical and Subantarctic Fronts, where the chlorophyll a concentrations were highest, the surface layer showed silicate depletion limiting diatom growth. South of the Subantarctic Front there were deep extending, low concentrations of chlorophyll a, but despite plentiful supplies of macro-nutrients and a well-stratified surface layer, high concentrations of chlorophyll a were absent. Changes from west to east were associated with the meandering of the Southern Ocean Fronts, especially the Subtropical Front, and their strength and proximity to each other. Concentrations of chlorophyll a peaked where the Agulhas Return, Subtropical and Subantarctic Fronts were in close proximity. Combined frontal structures appear to have particularly pronounced vertical stability and are associated with enhanced upwelling of nutrients and leakage of nutrients across the front. Light levels are high within the shallow stable layer. Such conditions are clearly favourable for biological growth and support the development of larger-celled phytoplankton communities. 相似文献
1000.