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1.
J. Dommanget 《Journal of Astrophysics and Astronomy》2003,24(3-4):99-109
A research that we conducted in 1963 on the evolution of the binaries based on the available orbital data to obtain a philosophical
degree, led to the establishment of an interesting and new diagram between the logarithm of the total mass and a particular
parameterX, bound to the areal constant. This appeared to have a real physical significance but the basic observational material was
insufficiently extended to assure its undeniable existence. In 1981, a new research based on a more extended orbital material,
has confirmed this diagram. Presently, another important increase in the orbital material and the availability of highly accurate
trigonometric parallaxes produced by the Hipparcos satellite, gave us the opportunity to confirm once more the stability of
this diagram. This last research is here described. 相似文献
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《Mathematical Geology》1997,29(5):653-668
Filtering either through the electronics of an instrument or through digital procedure is performed routinely on geophysical
data. When velocity fluctuations are measured in turbulent flows using electromagnetic current meters (ECMs), a builtin lowpass
Butterworth filter of order n usually attenuates fluctuations at high frequencies. However, the effects of this filter may
not be acknowledged in turbulence studies, thus impeding comparisons between data collected with different ECMs. This paper
explores the implications of the filters on the characteristics of velocity signals, mainly on variance, power spectra, and
correlation analyses. Variance losses resulting from filtering can be important but will vary with the order n of the Butterworth
filter, decreasing as n increases. Knowing the filter response, it is possible to reconstruct the original signal spectrum
to evaluate the effect of filtering on variance and to allow comparisons between data collected with different instruments.
The autocorrelation function also is affected by filtering which increases the value of the coefficients in the first lags,
resulting in an overestimation of the integral length scale of coherent structures. These important effects add to those related
to size and shape differences in ECM sensors and must be taken into account in comparative studies. 相似文献
6.
High-resolution paleoenvironmental data from a peat profile with a small pollen source area are used to reconstruct the impacts of landnám on vegetation and soils at a Norse farm complex (∅2 at Tasiusaq) comprising two farms in the Eastern Settlement of Greenland. Analyses include the AMS 14C dating of plant macrofossil samples and the use of Bayesian radiocarbon calibration to construct improved age-depth models for Norse cultural horizons. The onset of a regional landnám may be indicated by the clearance of Betula pubescens woodland immediately prior to local settlement. The latter is dated to AD 950-1020 (2σ) and is characterised by possible burning of Betula glandulosa scrub to provide grassland pasture for domestic stock. Clearance and grazing resulted in accelerated levels of soil erosion at a westerly farm. This was followed by an easterly migration of settlement and agriculture. Site constraints prevent an assessment of the demise of the easterly farm, but pressures of overgrazing and land degradation may have been the major factors responsible for the abandonment of the earlier farm. 相似文献
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The trend of previous estimates of the world's ultimate recovery of oil suggests a figure of 1650 BBO, of which 1438 BBO have been discovered and 978 BBO remain to be produced. Some large reported reserve figures are questioned. Importance is attached to the mid-point of depletion when rising production tends to give way to decline. The share of the world's supply coming from six Middle East countries is set to continue to rise from its 1986 low of 16% to as much as 50% by 2010, with the likely consequence of higher oil prices and serious political implications. The world is rapidly approaching a turning point when it has to face the consequences of an irreversible decline in oil production. 相似文献
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Two commonly used methods of simulating random time series, given a target power spectrum, are discussed. Wave group statistics, such as the mean length of runs of high waves, produced by the different simulation schemes are compared. The target spectra used are obtained from ocean measurements, and cover a wide range of ocean conditions. For a sufficiently large number of spectral components, no significant differences are found in the wave group statistics produced by the two simulation techniques. 相似文献
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本文在解放军土地管理局研制的“军用土地管理信息系统”的基础上,从系统设计和应用的角度出发,明确了系统应包括的基本功能,提出了改进和完善系统的方法。 相似文献