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991.
For the rising branch of Cycle 22, 1987 January—1989 November, we plot the daily total flux S at each of the five wavelengths 2.0, 3.4, 6.0, 10.7 and 21.2 cm against the apparent sunspot area of the dominant sunspot Ay and find that, for several large active areas, the locus is located below the average regression line, and the increase in the radio flux is insignificant compared to the increase in the sunspot area. 相似文献
992.
本文介绍了当今城市GPS应用的发展热点CORS系统的优势,并结合实例介绍了JSCORS RTK技术在某土方测量项目中的应用情况、作业流程,分析了测量时应该注意的问题。 相似文献
993.
Qi-Rong Yuan Peng-Fei Yan Yan-Bin Yang Xu Zhou Department of Physics Nanjing Normal University Nanjing yuanqirong@njnu. edu. cn National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Mathematics Physics Qingdao University of Science Technology Qingdao 《中国天文和天体物理学报》2005,5(2):126-136
Convincing evidence for a past interaction between the two rich clusters A399 and A401 was recently found in the X-ray imaging observations. We examine the structure and dynamics of this pair of galaxy clusters. A mixture-modeling algorithm was applied to obtain a robust partition into two clusters, which allowed us to discuss the virial mass and velocity distribution of each cluster. Assuming that these two clusters follow a linear orbit and they have once experienced a close encounter, we model the binary cluster as a two-body system. As a result, four gravitationally bound solutions are obtained. The recent X-ray observations seem to favor a scenario in which the two clusters with a true separation of 5.4h-1 Mpc are currently expanding at 583 km s-1 along a direction with a projection angle of 67.5°, and they will reach a maximum extent of 5.65 h-1 Mpc in about 1.0 h-1 Gyr. 相似文献
994.
995.
The possibility of using a nonlinear empirical atmospheric model for hybrid coupled atmosphere-ocean modelling has been examined
by using a neural network (NN) model for predicting the contemporaneous wind stress field from the upper ocean state. Upper
ocean heat content (HC) from a 6-layer ocean model was a better predictor of the wind stress than the (observed or modelled)
sea surface temperature (SST). Our results showed that the NN model generally had slightly better skills in predicting the
contemporaneous wind stress than the linear regression (LR) model in the off-equatorial tropical Pacific and in the eastern
equatorial Pacific. When the wind stresses from the NN and LR models were used to drive the ocean model, slightly better SST
skills were found in the off-equatorial tropical Pacific and in the eastern equatorial Pacific when the NN winds were used
instead of the LR winds. Better skills for the model HC were found in the western and central equatorial Pacific when the
NN winds were used instead of the LR winds. Why NN failed to show more significant improvement over LR in the equatorial Pacific
for the wind stress and SST is probably because the relationship between the surface ocean and the atmosphere in the equatorial
Pacific over the seasonal time scale is almost linear.
Received: 2 March 1999 / Accepted: 13 July 2000 相似文献
996.
997.
998.
The metric spectral data obtained at the Yunnan Observatory from July 1990 to December 1991 are analysed and some type III bursts associated with millisecond spikes are found. Their different morphologies reveal the relation between the type III bursts and the millisecond spikes. Based on the occurrence time and the characteristics of continuity and changes of the morphologies in the spikes and the type III bursts of two typical events, we verify that the acceleration region of the coronal electrons is located above the emitting region of the millisecond spikes and the type III bursts. The observations show that the interface frequency of a pair of type III bursts lies near 250 MHz. Finally the authors attempt to explain qualitatively the generating mechanism of the metric millisecond spike-type III bursts by means of the plasma hypothesis. 相似文献
999.
Dajun Tang Briggs K.B. Williams K.L. Jackson D.R. Thorsos E.I. Percival D.B. 《Oceanic Engineering, IEEE Journal of》2002,27(3):546-560
As part of the effort to characterize the acoustic environment during the high frequency sediment acoustics experiment (SAX99), fine-scale variability of sediment density was measured by an in situ technique and by core analysis. The in situ measurement was accomplished by a newly developed instrument that measures sediment conductivity. The conductivity measurements were conducted on a three-dimensional (3-D) grid, hence providing a set of data suited for assessing sediment spatial variability. A 3-D sediment porosity matrix is obtained from the conductivity data through an empirical relationship (Archie's Law). From the porosity matrix, sediment bulk density is estimated from known average grain density. A number of cores were taken at the SAX99 site, and density variations were measured using laboratory techniques. The power spectra were estimated from both techniques and were found to be appropriately fit by a power-law. The exponents of the horizontal one-dimensional (1-D) power-law spectra have a depth-dependence and range from 1.72 to 2.41. The vertical 1-D spectra have the same form, but with an exponent of 2.2. It was found that most of the density variability is within the top 5 mm of the sediment, which suggests that sediment volume variability will not have major impact on acoustic scattering when the sound frequency is below 100 kHz. At higher frequencies, however, sediment volume variability is likely to play an important role in sound scattering. 相似文献
1000.
Forty-eight surface sediments of the southern Yellow Sea are separated into three grain-size fractions. Four forms of extractable nitrogen (nitrogen in ion-exchangeable form (Nie), nitrogen in weak-acid extractable form (Nwa), nitrogen in strong-alkali extractable form (Nsa) and nitrogen in strong-oxidant form (N50))are obtained by the sequential extraction. The results show that the contents and the distributions of the extractable nitrogen in the southern Yellow Sea surface sediments are closely related to sediment grain size. The distributions ofNie, Nso and total nitrogen (TN) present positive correlations with fine particles content, while Nwa and Nsa does not have such correlation. The net contents of all the forms of nitrogen increase with sediment grain size finer. 相似文献