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101.
对华北地区韧性剪切带几种代表上、中、下地壳深度的糜棱岩及其围岩在高温高压条件下进行纵波速度测定及各向异性研究.对实验样品的纵波速度测定得到以下结果:1.沿糜棱岩面理方向的纵波速度大于与面理垂直方向的纵波速度,差值为0.15-0.30km/s,各向异性为3%-5%;2.糜棱岩的纵波速度低于其围岩的纵波速度,差值为0.10-0.45km/s;3.中地壳角闪岩相糜棱岩的纵波速度各向异性高于上地壳绿片岩相糜棱岩和下地壳麻粒岩相糜棱岩的各向异性;4.地震波速各向异性与糜棱岩矿物优选定向有关. 相似文献
102.
The analysis and interpretation of coda waves have received increasing attention since the early seventies. In the past few years interest in this subject has spread worldwide, and the study of high-frequency seismic coda waves has become a very important seismological topic. As a conclusion of the studies accomplished in this time, coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves.P andS waves play a particularly important role in this interaction. The process introduces an attenuation which, added to the intrinsic absorption, gives the observed apparent attenuation. Therefore, coda waves constitute a thumbprint left by the heterogeneities on the seismograms. Coda waves offer decisive information about the mechanism of how scattering and attenuation take place. This review describes coda waves in detail, and summarizes the work done in this subject to 1986. The relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed. Particular attention has been given to the application of coda waves to estimate source and medium parameters. The state-of-the-art of the temporal variations of coda wave shape, and the possible use of these variations as an earthquake precursor also are presented. Care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering. 相似文献
103.
Significant advances in flood inundation modelling have been made in the last decade through the use of a new generation of 2D hydraulic numerical models. These offer the potential to predict the local pattern and timing of flood depth and velocity, enabling informed flood risk zoning and improved emergency planning. With the availability of high resolution DEMs derived from airborne lidar, these models can theoretically now be routinely parameterized to represent considerable topographic complexity, even in urban areas where the potential exists to represent flows at the scale of individual buildings. Currently, however, computational constraints on conventional finite element and volume codes typically require model discretization at scales well below those achievable with lidar and are thus unable to make optimal use of this emerging data stream.In this paper we review two strategies that attempt to address this mismatch between model and data resolution in an effort to improve urban flood forecasts. The first of these strives for a solution by simplifying the mathematical formulation of the numerical model by using a computationally efficient 2D raster storage cell approach coupled to a 1D channel model. This parsimonious model structure enables simulations over large model domains offering the opportunity to employ a topographic discretization strategy which explicitly represents the built environment. The second approach seeks to further reduce the computational overhead of this raster method by employing a subgrid parameterization to represent the effect of buildings and micro-relief on flow pathways and floodplain storage. This multi-scale methodology enables highly efficient model applications at coarse spatial resolutions while retaining information about the complex geometry of the built environment.These two strategies are evaluated through numerical experiments designed to reconstruct a flood in the small town of Linton in southern England, which occurred in response to a 1 in 250 year rainfall event in October 2001. Results from both approaches are encouraging, with the spatial pattern of inundation and flood wave propagation matching observations well. Both show significant advantages over a coarse resolution model without subgrid parameterisation, particularly in terms of their ability to reproduce both hydrograph and inundation depth measurements simultaneously, without need for recalibration. The subgrid parameterization is shown to achieve this without contributing significant computational complexity and reduces model run-times by an order of magnitude. 相似文献
104.
Shin-Ichi Machida Hisako Hirai Taro Kawamura Yoshitaka Yamamoto Takehiko Yagi 《Physics and Chemistry of Minerals》2007,34(1):31-35
High-pressure Raman studies of methane hydrate were performed using a diamond anvil cell in the pressure range of 0.1–86 GPa
at room temperature. Raman spectra of the methane molecules revealed that new softened intramolecular vibration mode of ν
1 appeared at 17 GPa and that the splitting of vibration mode of ν
3 occurred at 15 GPa. The appearance of these two modes indicates that an intermolecular attractive interaction increases between
the methane molecules and the host water molecules and between the neighboring methane molecules. These interactions might
result in the exceptional stability of a high-pressure structure, a filled ice Ih structure (FIIhS) for methane hydrate, up
to 40 GPa. At 40 GPa, a clear change in the slope of the Raman shift versus pressure occurred, and above 40 GPa the Raman
shift of the vibration modes increased monotonously up to 86 GPa. A previous XRD study showed that the FIIhS transformed into
another new high-pressure structure at 40 GPa. The change in the Raman spectra at 40 GPa may be induced by the transition
of the structure. 相似文献
105.
106.
Accurate modeling of storage of carbon dioxide (CO2) in heterogeneous aquifers requires experiments of the capillary pressure as function of temperature and pressure. We present a method with which static drainage and imbibition capillary pressures can be measured continuously as a function of saturation at various temperature (T) and pressure (P) conditions. The measurements are carried out at (T, P) conditions of practical interest. Static conditions can be assumed as small injection rates are applied. The capillary pressure curves are obtained for the unconsolidated sand–distilled water–CO2 system. The experimental results show a decrease of drainage and imbibition capillary pressure for increasing CO2 pressures and pronounced dissolution rate effects for gaseous CO2. Significant capillary pressure fluctuations and negative values during imbibition are observed at near critical conditions. The measurement procedure is validated by a numerical model that simulates the experiments. 相似文献
107.
108.
云南蒙自五里冲水库岩溶及其工程处理 总被引:5,自引:3,他引:5
五里冲水库个旧组(T2^cg)灰岩,岩溶极其发育,其中尤以洼地深、峰丛高、溶洞多又大,地下河管道单一较长、岩溶总体发育历史悠久为特点,以更新世以来岩溶最为发育,现今地下河管道主要形成于晚更新世至今。因区域地壳持续抬升,岩溶没有成层发育的规律,但自上向下递减现象明显。工程上五里冲水库是以帷幕高压灌浆技术为主辅以其它多种方法处理溶洞及封堵地下河,利用天然盲谷成库的一座无大坝中型水库。帷幕高压灌浆技术先、便捷、可靠。水库蓄水己达设计水位,发挥了效益。一年可向蒙自县供水8161万m^3,可增加灌溉面积10万亩,改善灌溉2.3万亩,向城市及工业供水1210万m^3,使蒙自水利化程度由37%提高到70%以上。 相似文献
109.
目的:应用高分辨CT(HRCT)扫描方法,增加对头颅腔隙梗塞诊断的可靠性,材料和方法:对临床疑有腔隙的病人,在基底节区及可疑部位加用HRC扫描,遇到腔隙病灶与像素颗粒难以区分时在相同层面或上下1-2mm处做HRCT扫描。结果,有489例常规CT正常的病例哪现了腔隙灶,在遇到的502例不易诊断的可疑病灶中,经HRCT确诊的真正腔隙灶300例,伪腔隙(像素)202例,同时发现HRCT对正常脑组织结构的显示要较常规CT越得多,结论HRCT不仅能提高腔隙性梗塞的检出率,还能辨伪腔隙,是弥补常规CT对腔隙诊断不足的较好手段。 相似文献
110.