地震层析成像技术在黄花寨电站工程勘察中的应用     

熊勇 《贵州地质》2007,24(3):223-225,239

在受地形条件限制,开展地面物探勘察工作困难的地区,充分利用已有的平硐或钻孔地质工程,采用地震透射波层析成像技术进行勘察较为有利,勘察成果精度较高。文章结合工程实例,介绍利用地震层析成像技术查明岩溶、断层破碎带、强风化软弱夹层方面的应用。  相似文献   

Influence of shear speed and normal stress on the shear behavior and shear zone structure of granular materials in naturally drained ring shear tests     

Hiroshi Fukuoka  Kyoji Sassa  Gonghui Wang 《Landslides》2007,4(1):63-74

“Sliding Surface Liquefaction” is a process causing strength loss and consequent rapid motion and long runout of certain landslides. Using a new ring shear apparatus with a transparent shear-box and digital video camera system, shear-speed-controlled tests were conducted on mixed grains (mixture of three different sizes of sand and gravel) and mixed beads to study shear behavior and shear zone development process under the naturally drained condition in which pore pressure is allowed to dissipate through the opened upper drainage valve during shearing. Higher excess pore water pressure and lower minimum apparent friction were observed in the tests where grain crushing was more extensive under higher normal stress and higher shear speed. Along with the diffusion of silty water generated by grain crushing, smaller particles were transported upward and downward from the shear zone. Concentration of larger grains to the central and upper part of the shear zone was confirmed by means of visual observation together with grain size analysis of sliced samples from several layers after the test. On the other hand, smaller particles were accumulated mostly below the layer where larger grains were accumulated. The reason why larger grains were accumulated into the shear zone may be interpreted as follows: grains under shearing are also subjected to vertical movement, the penetration resistance of larger grains into a layer of moving particles is smaller than that into the static layer. Therefore, larger grains tend to move into the layer of moving grains. At the same time, smaller particles can drop into the pores of underlying larger grains downward due to gravity.  相似文献   

乌鲁木齐河源1号冰川不溶微粒的季节变化特征   总被引：12，自引：1，他引：12  

尤晓妮  李忠勤  王飞腾  朱宇曼 《地球科学进展》2006,21(11):1164-1170

冰芯中的不溶微粒是反映大气粉尘的良好指标，亦是冰芯定年的重要方法。为了探究不溶微粒在雪层中的季节变化特征，对采自乌鲁木齐河源1号冰川4 130 m处的雪冰样品进行不溶微粒分析。表层雪中粗微粒浓度在一年中有2个峰值，分别出现在12~3月、6~9月；总微粒只有一个峰值区，出现在4~8月。对比同期气象资料发现，其受降水、大气环流以及局地风影响显著。结合雪层物理剖面和微粒在雪层中的浓度发现：污化层是粗颗粒（直径大于10 μm）聚集的区域。对该粒径范围的微粒浓度峰值进行跟踪，发现不溶微粒在雪层中的浓度和位置变化与融水、物理成冰过程密切相关。  相似文献   

成都市大气可吸入颗粒物来源解析研究   总被引：7，自引：2，他引：7  

王淑兰  柴发合  周来东  王琴玲 《地理科学》2006,26(6):717-721

通过对成都市能源结构及产业布局的分析,对可吸入颗粒物来源进行了定性识别和分类,确定了对可吸入颗粒物可能产生贡献的源类的化学成分谱,用化学质量平衡受体模型(CMB)对成都市可吸入颗粒物的来源进行定量解析,确定了成都市PM10的主要来源。  相似文献   

北京市大气细粒子质量浓度与能见度定量关系初探   总被引：45，自引：3，他引：45  

王京丽  刘旭林 《气象学报》2006,64(2):221-228

北京近年的监测结果表明,大气中通过消光作用使大气能见度下降的气溶胶细粒子的污染水平呈现上升趋势。中国气象局北京城市气象研究所与北京大学合作于2001年春季(3月)、夏季(6月)、秋季(9月)和冬季(12月)开展了大气细粒子与气象能见度的同步综合观测,旨在探求细粒子的物理化学特征及其与大气能见度的关系。监测结果表明,能见度与PM2.5质量浓度在春季呈乘幂关系;夏季除高相对湿度外,呈指数关系;秋季呈对数关系;冬季呈指数关系。为了便于比较,将两者间的关系全部用指数关系表示。北京市大气能见度与细粒子质量浓度呈现很好的负相关性,无疑细粒子污染是造成大气能见度下降的主要原因,它已成为目前中国大气污染研究的重要内容之一。  相似文献   

Aerosol bacteria over the Southern Ocean during ACE-1     

Mihly Psfai  Jia Li  James R. Anderson  Peter R. Buseck 《Atmospheric Research》2003,66(4):231

Individual bacterial cells occur in many samples that were collected at Cape Grim, Tasmania and during the Lagrangian “B” experiment of the Aerosol Characterization Experiment 1 (ACE-1) campaign that was conducted above the Southern Ocean. They are present in samples from altitudes as high as 5.4 km. Morphologically, almost all bacteria are rod-shaped, about 1 μm long or smaller, have one polar flagellum, and contain inclusions that are rich in P and K. Their morphological features suggest that these bacteria are motile, marine species. It seems likely that the cells became airborne by the same bubble-bursting mechanism that ejects sea-salt aerosol particles into the atmosphere; however, the bacteria and sea-salt particles are typically not aggregated with one another. The estimated number ratio of bacteria and the dominant aerosol species, sea salt, varies in the samples and averages about 1%. The aerosol bacteria seem to represent an important atmospheric reservoir of P and organic compounds; on the other hand, since they are externally mixed with sea salt, they are unlikely to be effective as cloud condensation nuclei.  相似文献   

Turbulent “Dynamo” in the Passive Scalar Problem     

Elperin  T.  Kleeorin  N.  Rogachevskii  I. 《Studia Geophysica et Geodaetica》1998,42(3):436-444

A turbulent magnetic dynamo can be considered as the evolution of a vector field in a turbulent fluid flow. The problem of evolution of scalar fields (e.g., number density of small particles) in a turbulent fluid flow is similar to the turbulent magnetic dynamo. The dynamo instability results in generation of magnetic field. The most important effect which can cause a generation of mean magnetic field in a turbulent fluid flow is the -effect: = – (1/3) u · ( × u), where u is the turbulent velocity field with the correlation time . A similar instability in the passive scalar problem results in formation of large-scale inhomogeneous structures in a spatial distribution of particles due to the -effect: = u_p ( · u_p), where u _p is the random velocity field of the particles which they acquire in a turbulent fluid velocity field. The effect is caused by inertia of particles which results in divergent velocity field of the particles. This results in additional turbulent nondiffusive flux of particles. The mean-field dynamics of inertial particles are studied by considering the stability of the equilibrium solution of the derived evolution equation for the mean number density of the particles in the limit of large Péclet numbers. The resulting equation is reduced to an eigenvalue problem for a Schrödinger equation with a variable mass, and a modified Rayleigh-Ritz variational method is used to estimate the lowest eigenvalue (corresponding to the growth rate of the instability). This estimate is in good agreement with obtained numerical solution of the Schrödinger equation. Similar effects arise during turbulent transport of gaseous admixtures (or light noninertial particles) in a low-Mach-number compressible fluid flow. The discussed effects are important in planetary and atmospheric physics (cloud formation, pollutant dynamics, preferential concentration of particles in protoplanetary disks and also planetesimals in them).  相似文献   

Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas     

F. Fécan  B. Marticorena  G. Bergametti 《Annales Geophysicae》1998,17(1):149-157

Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension) are the main factor responsible for the increase of the wind erosion threshold observed when the soil moisture increases. When the soil moisture content is close to but smaller than the maximum amount of adsorbed water, w′ (depending on the soil texture), these capillary forces are considered as not strong enough to significantly increase the erosion threshold. An expression of the moisture tension as a function of soil moisture and w′ is derived from retention curves. From this expression, a parametrization of the ratio of the wet to dry erosion thresholds has been developed as a function of soil moisture and soil texture. The coefficients of this parametrization have been determined by using experimental data from the literature. An empirical relationship between w′ and soil clay content has been established. The erosion threshold ratios simulated for different soil textures were found to be in good agreement with the experimental data.  相似文献   

The ion experiment onboard the Interball-Aurora satellite; initial results on velocity-dispersed structures in the cleft and inside the auroral oval     

J. A. Sauvaud  H. Barthe  C. Aoustin  J. J. Thocaven  J. Rouzaud  E. Penou  D. Popescu  R. A. Kovrazhkin  K. G. Afanasiev 《Annales Geophysicae》1998,16(9):1056-1069

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A quantitative model for cyclotron wave-particle interactions at the plasmapause     

D. L. Pasmanik  V. Y. Trakhtengerts  A. G. Demekhov  A. A. Lyubchich  E. E. Titova  T. Yahnina  M. J. Rycroft  J. Manninen  T. Turunen 《Annales Geophysicae》1998,16(3):322-330

The formation of a zone of energetic electron precipitation by the plasmapause, a region of enhanced plasma density, following energetic particle injection during a magnetic storm, is analyzed. Such a region can also be formed by detached cold plasma clouds appearing in the outer magnetosphere by restructuring of the plasmasphere during a magnetic storm. As a mechanism of precipitation, wave-particle interactions by the cyclotron instability between whistler-mode waves and electrons are considered. In the framework of the self-consistent equations of quasi-linear plasma theory, the distribution function of trapped electrons and the electron precipitation pattern are found. The theoretical results are compared with experimental data obtained from NOAA satellites.  相似文献