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121.
122.
高岭石—莫来石反应系列:^27Al和^29SiMAS NMR研究 总被引:21,自引:2,他引:21
根据艰我国八个不同成因和特征的高岭土样品在450-1450℃热处理产物的MAS NMR谱和XRD,IR,DTA等研究结果,结合有关资料讨论了高岭石-莫来石反应序列的几个重要问题:1.高岭石的结构,尤其是五配位铝;2.980℃放热峰后的高温相是γ-Al2O3而不是Al-Si尖晶石;3.对于莫来石化过程,认为初始莫来石850-950℃变高岭石形成,二次莫来石由分凝的SiO2和γ-Al2O3在1200- 相似文献
123.
Noise reduction and detection of weak, coherent signals through phase-weighted stacks 总被引:10,自引:0,他引:10
We present a new tool for efficient incoherent noise reduction for array data employing complex trace analysis. An amplitude-unbiased coherency measure is designed based on the instantaneous phase, which is used to weight the samples of an ordinary, linear stack. The result is called the phase-weighted stack (PWS) and is cleaned from incoherent noise. PWS thus permits detection of weak but coherent arrivals. The method presented can easily be extended to phase-weighted cross-correlations or be applied in the τ p domain. We illustrate and discuss the advantages and disadvantages of PWS in comparison with other coherency measures and present examples. We further show that our non-linear stacking technique enables us to detect a weak lower-mantle P -to- S conversion from a depth of approximately 840 km on array data. Hints of an 840 km discontinuity have been reported; however, such a discontinuity is not yet established due to the lack of further evidence. 相似文献
124.
Using surface charts at 0330GMT, the movement of the monsoon trough during the months June to September 1990 at two fixed
longitudes, namely 79°E and 85°E, is studied. The probability distribution of trough position shows that the median, mean
and mode occur at progressively more northern latitudes, especially at 85°E, with a pronounced mode that is close to the northern-most
limit reached by the trough. A spectral analysis of the fluctuating latitudinal position of the trough is carried out using
FFT and the Maximum Entropy Method (MEM). Both methods show significant peaks around 7.5 and 2.6 days, and a less significant
one around 40–50 days. The two peaks at the shorter period are more prominent at the eastern longitude. MEM shows an additional
peak around 15 days. A study of the weather systems that occurred during the season shows them to have a duration around 3
days and an interval between systems of around 9 days, suggesting a possible correlation with the dominant short periods observed
in the spectrum of trough position. 相似文献
125.
Multifractal modeling and spatial statistics 总被引:9,自引:0,他引:9
In general, the multifractal model provides more information about measurements on spatial objects than a fractal model. It also results in mathematical equations for the covariance function and semivariogram in spatial statistics which are determined primarily by the second-order mass exponent. However, these equations can be approximated by power-law relations which are comparable directly to equations based on fractal modeling. The multifractal approach is used to describe the underlying spatial structure of De Wijs 's example of zinc values from a sphalerite-bearing quartz vein near Pulacayo, Bolivia. It is shown that these data are multifractal instead of fractal, and that the second-order mass exponent (=0.979±0.011 for the example) can be used in spatial statistical analysis. 相似文献
126.
波,流联合作用下的近岸海底沙波稳定性研究进展 总被引:3,自引:0,他引:3
近岸海底大型沙波是一种研究较为薄弱的地貌单元,但它的迁移对港口、航道和海底电缆及钻井平台、输油管道等海洋工程设施建设造成的危害极大。在综述目前国内外有关研究文献的基础上,概要地介绍了作者提出的一种较为简便、省力和有效的沙波迁移速率和沙波稳定性定量评价和预测方法,旨在提高航道通航能力和海洋工程建设的灾害防治和预测能力 相似文献
127.
试论HACSAMT法 总被引:3,自引:0,他引:3
HACSAMT法在不增加任何设备、工作人员、工作时间的前提下,观测基波信号的同时,采集其高次谐波的振幅和相位的数据,大大地提高了劳动效率,而且,由于运用了谐波的有用信号,加密了CSAMT法勘探的频率,从而,提高了CSANT法的纵向勘探分辨率 相似文献
128.
根据矿田内岩矿地质波谱与TM图象亮度的线性相关关系,论述了多宝山铜矿田内矿床的地面波谱特征,地空相关模型及TM数据的地空相关分析方法,在此基础上讨论了其在铜矿预测中的应用效果。 相似文献
129.
130.
Federico Murrone Fabio Rossi Pierluigi Claps 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(6):483-510
A conceptual-stochastic approach to short time runoff data modelling is proposed, according to the aim of reproducing the
hydrological aspects of the streamflow process and of preserving as much as possible the dynamics of the process itself. This
latter task implies preservation of streamflow characteristics at higher scales of aggregation and, within a conceptual framework,
involves compatibility with models proposed for the runoff process at those scales. At a daily time scale the watershed response
to the effective rainfall is considered as deriving from the response of three linear reservoirs, respectively representing
contributions to streamflows of large deep aquifers, with over-year response lag, of aquifers which run dry by the end of
the dry season and of subsurface runoff. The surface runoff component is regarded as an uncorrelated point process. Considering
the occurrences of effective rainfall events as generated by an independent Poisson process, the output of the linear system
represents a conceptually-based multiple shot noise process. Model identification and parameter estimation are supported by
information related to the aggregated runoff process, in agreement to the conceptual framework proposed, and this allows parameter
parsimony, efficient estimation and effectiveness of the streamflow reproduction. Good performances emerged from the model
application and testing made with reference to some daily runoff series from Italian basins. 相似文献