结合水对海积软土流变性质的影响

海积软土的变形和强度性质与时间有明显的相关性，其原因之一是其中含量较多的结合水。土在一定压力下先排出自由水，然后是结合水，结合水膜厚度发生改变。压力改变结合水膜厚度，引起粘滞系数改变。通过剪切增变试验得到了粘滞系数与压力呈线性关系。研究粘滞系数与压力之间关系对修正或建立较为符合实际的本构模型有一定意义。     

Electrical conductivity problems associated with time-domain reflectometry (TDR) measurement in geotechnical engineering

The effect of electrical conductivity (EC) of a dielectric material on its TDR-measured dielectric constant ε_a (called the apparent dielectric constant) was investigated both theoretically and experimentally. The effect of EC on the apparent dielectric constant ε_a was more pronounced at low frequency of the electromagnetic pulse applied to measure ε_a. The assumption of neglecting electrical losses in measuring the dielectric constant by TDR to represent ε_r was not valid for dielectric materials containing free charges, such as electrolyte solutions, bentonite clay, and saline soils. A theory is proposed to separate the real part of the dielectric constant ε_r from the TDR-measured ε_a in lossy dielectrics. An EC - ε_r relationship can be developed that would provide ε_a (=ε_r) at EC = 0 to be used to determine soil-water contents in conductive soils. Na-bentonite mixed with distilled water resulted in considerable magnitude of bulk EC due to the adsorbed cations on the surface of the particles. This EC caused energy loss of the TDR pulse that depended on the length of the probe rod. For a 4.5 cm long probe, the reflected TDR waveform was completely attenuated for EC between 3.05 dS m⁻¹ and 3.72 dS m⁻¹. The waveforms generated in this range of EC were not suitable for analysis by TDR-support software for dielectric constant. With the adsorbed cations, Na-bentonite behaved as a lossy or dispersive material. This revised version was published online in July 2006 with corrections to the Cover Date.     

数字地震仪原理及频率响应函数和传递函数——地震学上用的数字信号处理的基本原理与实例(讲座2)

将一般线性时间不变系统的概念和分析方法运用到经典摆式地震仪中,并通过地震仪的频率响应函数和传递函数的分析,更好地理解为了获得真实的地面运动记录,应对原始数字化地震记录进行仪器修正的必要性。     

多频电磁波测井的数值模拟

从麦克斯韦方程及本构关系出发,导出了频率域中的电磁波动方程。采用有限差分方法,对波动方程求数值解。设计的程序可模拟实际的测井过程。程序执行后给出模拟测井曲线。数值模拟试验表明,多频电磁波测井对区分油水层是成功和有效的。     

非磁化吸积盘中的粘滞性和朗缪尔波湍动应力

粘滞性问题一直是吸积盘理论中十分重要而又难以解决的一个基本理论问题．最近,Balbus和Hawley建议在磁化吸积盘中存在一种局域的磁流体剪切不稳定性机制,它能导致磁化吸积盘中有效的角动量转移,从而可以部分地解决磁化吸积盘中的粘滞性问题．但是Balbus－Hawley机制对非磁化吸积盘仍然是无效的．在本文中,我们研究了一种非磁化吸积盘模型,其中粘滞性机制起源于等离子体朗缪尔波湍动应力,并与标准a吸积盘模型中起源于流体或磁流体湍流的雷诺应力的粘滞性机制进行了比较．结果表明等离子体朗缪尔波湍动应力不仅对非磁化吸积盘中粘滞性的起源有重要的贡献,而且有可能是比流体湍流或磁流体湍流的雷诺应力更加有效的粘滞性起源的物理机制．     

漫滩水流摩阻因子与涡粘性系数的研究

对复式河道漫滩水流进行了研究,建立了摩阻因子与一维明渠流摩阻因子的关系,揭示出滩地的量纲为一涡粘性系数随着摩阻因子的增加而增加,并将二次流的影响表达成与雷诺切应力相同的形式,从而将其归入表观切应力中,由量纲为一表观涡粘性系数确定,后者可通过量纲为一表观涡粘性系数与摩阻因子之间的一个关系加以计算,该关系类似于量纲为一涡粘性系数与摩阻因子之间的关系。对光滑边界上对称的漫滩水流进行了计算,计算结果与实验资料吻合良好。     

Lateral variation in upper mantle viscosity: role of water

Differences in the viscosity of the earth's upper mantle beneath the western US (∼10¹⁸-10¹⁹ Pa s) and global average values based on glacial isostatic adjustment and other data (∼10²⁰-10²¹ Pa s) are generally ascribed to differences in temperature. We compile geochemical data on the water contents of western US lavas and mantle xenoliths, compare these data to water solubility in olivine, and calculate the corresponding effective viscosity of olivine, the major constituent of the upper mantle, using a power law creep rheological model. These data and calculations suggest that the low viscosities of the western US upper mantle reflect the combined effect of high water concentration and elevated temperature. The high water content of the western US upper mantle may reflect the long history of Farallon plate subduction, including flat slab subduction, which effectively advected water as far inland as the Colorado Plateau, hydrating and weakening the upper mantle.     

Turbulent viscosity measurements relevant to planetary core-mantle dynamics

Laboratory experiments that combine thermal convection in a rapidly rotating shell with a sudden increase of the shell’s rotation rate (spin-up) enable us to study processes related to turbulent viscous coupling between planetary fluid cores and solid mantles. We experimentally measure the large-scale effective viscosity by determining how the synchronisation time between the fluid and the shell (called the spin-up time) is shortened when convective turbulence exists in the bulk of the fluid. Our experiments suggest that viscous core-mantle coupling in planets may be greater than has been previously estimated using molecular viscosity values.