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471.
Downburst is a very dangerous weather phenomenon for aeroplane taking off or landing. In order to understand the initial formation and evolution of downburst and to study the effects of atmospheric environment condition and the microstructure of cloud-precipitation particles on the downburst development processes, we have designed and carried out a modeling scheme by making use of our own non-hydrostatic compressible mesoscale-γ model including necessary cloud-precipitation processes. The initial conditions of temperature, humidity and wind are from an observation case in which the downburst occurred. The results of computations demonstrate the evolution of downburst and show the variation of various environmental and microphysical parameters. Some of the mechanisms about the downburst occurrence have been obtained. Computation results may help airport forecasters to determine the occurrence of downburst better. 相似文献
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The microstructure charateristics of illite from the Chuanlinggou Formation of Changcheng System (Chch) in Jixian County, Tianjin City has been studied by means of high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray energy dispersive spectrum (EDS) and X-ray powder diffraction (XRD). The Kübler index of "illite crystallinity" is 0.505°△2θ, which indicates that the host rock is in a middle diagenetic stage. The chemical analyses of EDS for illite studied indicate a heavily absent in interlayer cation and an average chemical formula of K0.57(Al1.80Mg0.42Fe2 0.12)Σ=2.34 (Si2.92Al1.08)Σ=4O10(OH)2. It is found, from one-dimensional lattice images, that the layers of illite not only stack in a flat way but also in a curving way. A "matting fabric" illite structure results from stacking faults. Combined with SAED analysis the illite studied can be affirmed as 1M illite. The two-dimensional lattice images are obtained from [100] and [110] incidences, whose lattice images have the same d-values but different intersecting angles. The two-dimensional lattice image with [100] incidence is orthogonal to each other, whilst that with [110] incidence is oblique. This paper provides some important structure information of authigenic clay minerals for the well-known mesoproterozoic section of Jixian County. 相似文献
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S. WALLIS 《Journal of Metamorphic Geology》1998,16(1):83-95
Tectonic processes that have been proposed to explain the transport to the surface of regional metamorphic belts can be broadly divided into two types. (i) Corner-flow within a convergent margin bounded by two essentially rigid plates associated with extension at shallow levels. This type of model assumes deformation is distributed throughout the margin and that any discontinuities are of secondary importance. (ii) Expulsion or extrusion of coherent metamorphic nappes. In this second idea, tectonic discontinuities are fundamental in the transport to the surface of metamorphic rocks. The wealth of geological data available from a variety of studies in the Sanbagawa metamorphic belt, southwest Japan makes it well-suited for studying the relative importance of continuous vs. discontinuous deformation in the process of exhumation. In the Sanbagawa belt a sudden decrease in metamorphic pressure going down section of several kilobars suggests the presence of a major tectonic contact separating two major regional nappes: an overlying higher-pressure Besshi nappe and an underlying lower-pressure Oboke nappe. Major tectonic discontinuities have also been proposed within the Besshi nappe, however, indicators of metamorphic temperature, the results of radiometric age dating, and microstructural studies all suggest that post-metamorphic discontinuities are minor and that this nappe formed and remained as an essentially coherent unit. Lithological associations and petrological studies suggest the following positions for the two nappes. The Besshi nappe formed deep within the former accretionary wedge, adjacent to the overlying mantle wedge, and with a dip of roughly 30 °C. In contrast, the Oboke nappe formed at moderate depths within the accretionary wedge, was distant from the mantle wedge, and was roughly horizontal. Penetrative deformation that post-dates the peak of metamorphism has affected nearly all of the Sanbagawa belt and has played an important role in its exhumation. However, the presence of a broad coherent Besshi nappe overlying the lower-pressure Oboke nappe suggests that some process such as buoyancy-driven extrusion was also important in the exhumation process and in forming the structure of the Sanbagawa metamorphic belt. 相似文献
478.
碱性长石Al—Si有序化进程中微结构和^29Si NMR谱的表现 总被引:2,自引:0,他引:2
笔者用X射线粉末衍射技术,对六个天然钾长石中的铝在T1O四面体位置的占位率进行了测定,它们的T1O值从0.28变化到0.79。对它们的透射电子显微镜研究表明,两个T1O为0.28和0.31的高透长石有对电子束异常过敏的调制结构,无法记录到它们的衍射像,在另外三个样品中,都见到芦席状结构,并夹杂着具一定宽度的片晶组成的格子双晶。片晶宽度随T1O的变大而增加。而在产于一个霞石正长岩中的正长石中没有观察 相似文献
479.
笔者对产于山东五莲县七宝山辉石二长岩中的碱性长石进行了电子探针,X射线衍射,透射电子显微镜以及^29SiMASNMR谱研究,确定五莲碱性三元长石(Or50.3,Ab44.3An5.4)为钾长石和钠长石共格出溶连晶,其基体钾长石为单斜对称,在透射电子显微镜下未见其呈现任何微结构,而在钠长石中见到宽度为10.4nm(钠长石的8b0)的片晶相互形成周期钠长石律双晶,钠长石叶片的宽度平均为39nm(n=4 相似文献
480.
固化软土微观结构效应 总被引:8,自引:0,他引:8
为了尽快提高地基加固的效率,对吹填土采用水泥和石灰进行快速加固,对加入添加剂固化后吹填土的微观结构应用计算机图像处理技术进行了定量分析,得出了袁征结构单元体和孔隙大小、形态及定向性等结构要素的定量评价指标.不同的添加剂含量对结构单元体大小的影响较大,当水泥掺入比为15%而石灰的掺入比为20%时,添加剂的胶结作用表现最好;添加剂的加入使得孔隙变小,结构变得比较致密,固化后土体强度得到了一定提高. 相似文献