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121.
在系统地分析了目前各种测震学地震预报方法科学思路的基础上,认为测震学地震预报方法基本上可以分为两大类。一类是以已经发生的一些地震作为未来可能发生的地震的“因”,即由于已经发生的地震对区域应力场的影响,导致未来发生较强地震。这一类包括的预报方法较多,如空区、条带、b值、地震迁移、相关地震等等及其由此衍生出来的各种方法。另一类是把已经发生的一些地震作为区域应力场增强的“果”,即已经发生的地震是区域应力场增强过程中的一种反映,而未来地震不一定是已经发生的地震所导致的结果。这一类包括“地震窗口”、小震群活动等方法。针对第一类方法,各种预报方法都是力图从地震三要素中提取未来地震的信息,而具体作法又都是利用地震三要素这个多维空间的某个剖面。为了从地震活动诸要素的多维空间提取综合信息,我们对每个地震加入了破裂面方位,构成了地震第四要素,并依据地震4要素建立了地震综合效应场函数。地震综合效应场函数概括了多种测震学地震预报方法的科学思路和预报经验,从而可以形成测震学的综合预报方法。 相似文献
122.
We analysed the atmospheric total column ozone temporal and spatial distributions,by using the USA Nimbus Satellite TOMS data provided by the Goddard Space Flight Center of NASA,USA.We ploted the monthly mean total column ozone distributions over China by the averaged data from 1979 to 1991,and found that the atmospheric total column ozone contours were parallel to latitudes in winter and spring. However, from June, the lower center of atmospheric column ozone, called "ozone valley",was formed gradually over the Tibetan Plateau, as shown in Fig. 相似文献
123.
124.
Porous fence is a kind of artificial windbreak that has many practical applications. The threshold wind velocities at different distances downwind from porous fences were measured and the corresponding characteristics of particle movement observed to assess their shelter effect. It is found that the fence’s porosity is the key factor that determines the resulting shelter effect. The area near a fence can be typically classified into five regions, each with a different mode of particle movement. Dense fences, and especially solid fences, favor the accumulation of sand upwind of the fences. Fences with porosities of 0.3–0.4 produce the maximum threshold wind velocity; those with porosities of 0.3–0.6 (depending on the fence height) provide the maximum effective shelter distance. It is confirmed that the fence porosities of 0.3–0.4 that have been proposed for practical application in previous research are the most effective for abating wind erosion. 相似文献
125.
我国煤炭资源开发利用中某些问题的探讨 总被引:3,自引:0,他引:3
针对我国煤炭资源开发利用中存在的诸如煤炭资源的低效率应用、无序开采、生态环境恶化等问题,指出了我国煤炭资源管理法规中存在的问题,提出了加强煤炭资源开发管理、构建煤炭循环经济体系、加大安全投入、加强煤炭矿区环境的治理和保护、健全有偿使用资源法规制度等对策。 相似文献
126.
127.
本对斜交型扰动不稳定谱点的分布做了理论分析,得到了该谱点分布的半圆定理一该谱点分布在复一面上以原点为圆心以R0为半径的上半平面上,同时还对该不稳定增长率的上界作了估计。发现水平永度越小,模式顶越高则该估计值越大;垂直风切变的增大和纬度的增高对该增长率的增大有正贡献;当层结稳定度减小时,最大增长率随相对最大增长率得增大而减小。 相似文献
128.
通过引人泊松括号,分析了无限维Hamilton的性质,并将其推广到广义Hamilton系统,且从理论和实用角度讨论了这类广义Hamilton系统的辛格式构造问题,从而为辛几何算法在一般的时间发展方程的数值求解提供新的具体途径。 相似文献
129.
A. K. Varma R. M. Gairola A. K. Mathur B. S. Gohil Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):247-256
In this paper, MSMR geophysical products like Integrated Water Vapour (IWV), Ocean Surface Wind Speed (OWS) and Cloud Liquid
Water (CLW) in different grids of 50, 75 and 150 kms are compared with similar products available from other satellites like
DMSP-SSM/I and TRMMTMI. MSMR derived IWV, OWS and CLW compare well with SSM/I and TMI finished products. Comparison of MSMR
derived CLW with that derived from TMI and SSM/I is relatively in less agreement. This is possibly due to the use of 37 GHz
in SSM/I and TMI that is highly sensitive to CLW, while 37 GHz channels are not available on MSMR. Monthly comparison of MSMR
geophysical products with those from TMI is all carried out for climatological purpose. The monthly comparisons were much
better compared to instantaneous comparisons. In this paper, details of the data analysis and comparison results are presented.
The usefulness of the MSMR vis-à-vis other sensors is also discussed. 相似文献
130.
Peter G. Verity 《Estuaries and Coasts》2002,25(5):944-960
The Skidaway River estuary is a tidally-dominated subtropical estuary in the southeastern USA surrounded by extensiveSpartina salt marshes. Weekly smapling at high and low tide began in 1986 for hydrography, nutrients, chlorophylla, particulate matter, and microbial and plankton biomass and composition; hydrographic and nutrient data during 1986–1996
are reported here. Salinity varied inversely with river discharge and exhibited variability at all time scales but with no
long-term trend. Water temperature typically ranged over 25°C and was without apparent long-term frend. Seasonal cycles in
concentrations of NO3, NH4, PO4, Si(OH)4, and DON were observed, with annual maxima generally occurring in late summer. Superimposed on seasonal cycles, all five
nutrients exhibited steady increases in minimum, mean, and maximum concentrations; mean concentrations increased c. 50–150%
during the decade. Nutrient concentrations were highly correlated with water temperature over the ten-year period, but weakly
related to salinity and discharge. Nutrients were strongly correlated with one another, and the relative ratios among inorganic
nutrients showed little long-term trend. Correlations among temperature and nutrient concentrations exhibited considerable
inter-annual variability. Major spikes in organic and inorganic nutrient concentrations coincided with significant rainfall
events; concentrations increased hyperbolically with rainfall. Although pristine compared to more heavily impacted waterways
primarily outside the region, residential development and population density have been increasing rapidly during the past
15–20 years. Land use is apparently altering nutrient loading over the long-term (months-years), and superimposed on this
are stochastic meteorological events that accelerate these changes over the short term (days-weeks). 相似文献