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901.
902.
本文用近13年200hPa高空风资料得到了夏半年(5—10月)逐月平均全球热带风场,发现如下一些主要结果: (1)在亚洲地区对流层上部反气旋存在两个中心;一个在青藏高原上空;一个在伊朗和阿富汗地区。两者的演变不同。伊朗高压的北推和撤退都比青藏高原上的早。北美墨西哥高压的变化在时间上与伊朗高压很相似。 (2)北太平洋中部高空槽(TUTT)出现在5—10月,8月份最强,位置最北;北大西洋中部高空槽出现在5—9月,7—8月最强。 (3)南半球冬季有三个主要的长波脊和长波槽,分别位于大陆以西和以东海区。 相似文献
903.
In this paper, Wu and Blumen’s boundary layer geostrophic momentum approximation model (Wu and Blumen, 1982) is applied to baroclinic and non-neutral PBL, the motion equations for the PBL under the geostrophic momentum approximation are solved, in which the eddy transfer coefficient is a function of the distributions of the wind and temperature. The results are compared with those in barotropic and neutral conditions with the geostrophic momentum approximation. It is found that in the baroclinic condition, the wind distribution has both the characteristics of a steady, homogeneous and baroclinic PBL and those caused by the geostrophic momentum approximation. Those in non-neutral conditions show that they retain the intrinsic characteristics for the wind in non-neutral PBL, at the same time, the effects of the large-scale advection and local variation are also included. We can predict the wind in the non-neutral and baroclinic PBL by use of the geostrophic mo-mentum approximation when the temporal and spatial distributions of the geostrophic wind, as well as the po-tential temperatures and their variation rates at the upper and lower boundary of the PBL are given by large-scale model. Finally, the model is extended to the case over sea surface. 相似文献
904.
905.
The properties of rock resitivity were studied under pressure, particularly with “stress reversal”, a procedure in which the
pressure applied was increased and decreased.
It was observed that, 1) With pressure increasing, the main feature of resistivity change was increase-steady-decrease for
high-saturation rock samples (saturation 70–100%). But the main feature for low-saturation samples was different. 2) In 10
out of 11 cases of “stress reversal” for high-saturation samples the resistivity droped (about 2%). Such drop could explain
the anomalies in geoelectricity terms, which are commonly observed before earthquakes in China. 3) It was also observed shortly
before rock failure that, a) the resistivity drops more dramatically (about 20%) during “stress reversal” period, which is
much more than ordinary drops. b) these drops occurred not only during stress decrease but also during stress increase. c)
Resistivity exhibits anisotropy: the resistivity along different directions may differ by 10%. These three features may indicate
that the rock is nearing failure, while ordinary resistivity drops are only connected with “stress reversal” and may not mean
the imminence of rock failure. 4) Resistivity increase was observed during the “stress reversal” period for low-saturation
rock samples.
The results mentioned above were explained with the effect of water flowing in and out of the cracks of rock. The temporary
factors which yield a reduction of the maximum main stress, may enhence the possibility of earthquake occurrence. 相似文献
906.
勘探工程地质统计信息法 总被引:2,自引:0,他引:2
勘探工程地质统计信息法试图运用定量评价准则研究勘探工程,而定量评价准则是建立在矿体数学模型基础上。本文在最优勘探方案和最优工程位置选择方面作了一些研究。 相似文献
907.
908.
应力波在波阻抗连续变化的弹性杆中的演化 总被引:2,自引:2,他引:2
利用特征线方法数值模拟计算了应力波在截面或弹性模量连续变化的弹性杆中的反射,同时也讨论了应力波脉冲宽度对反射波波形特征的影响,其结果对桩基测量有一定的参考价值。 相似文献
909.
910.