Improvements in Inversion of Magnetic Resonance Exploration-Water Content, Decay Time, and Resistivity

In this review article, we present recent developments and Improvements in magnetic resonance sounding (MRS), a newly established geophysical exploration method that provides unique information about hydrogeophysical properties due to its direct sensitivity to hydrogen protons and proton dynamics. Starting with the most sophisticated and complete MRS formulation, we give a detailed view on how to solve the equation, i.e., inverting exactly for all model parameters: water content, decay time, and resistivity. Giving a short review of general inversion schemes used in geophysics, the special properties of MRS inversion are evaluated and the development of MRS inversion over recent years is shown. We present the extension of MRS to magnetic resonance tomography (MRT), i.e., the extension to two-dimensional investigations and appropriate inversions. Finally, we address restrictions, limitations, and inconsistencies as well as future developments.     

红砂岩吸水软化及冻融循环力学特性劣化

水与温度变化是工程岩石物理力学性能劣化的典型风化因素。对不同含水状态及经受不同次数冻融循环损伤后的红砂岩岩样进行了单轴压缩、劈裂拉伸及变角剪切试验。结果表明,红砂岩抗压强度、弹性模量、劈拉强度、黏聚力及内摩擦角等主要力学指标随含水率和冻融循环次数的增大均有不同程度的降低,但降低规律有所不同。水对岩石有明显的软化作用,冻融循环累积损伤显著。利用微观电镜扫描分析了不同含水率及冻融损伤后岩样微观结构的变化规律,认为吸水及冻融循环过程中水对红砂岩的软化表现为溶蚀作用与介质作用,温度变化的作用表现在热变形不协调和相变作用。提出了冻融循环作用下红砂岩力学特性衰减模型,并据此分析了各力学指标的衰减速率和半衰期。该研究结果对涉水岩石工程及寒区岩石工程具有一定的意义。     

Asymptotic behaviour of decay rates of internal waves in a rotating stratified spherical shell

Summary. Boundary layer techniques are used to examine the dissipative decay of an internal oscillation that is a member of the inviscid spectrum of normal modes for a rotating fluid shell stratified under a radially directed gravitational field. A formula is derived for the decay factor on the so-called homogeneous spin-down time-scale. Estimates are obtained for the size of the decay factor as a function of wavelength, a function of the frequency and a function of a parameter A which measures the ratio of the stratification strength to the rotation strength. It is shown that all modes decay on the spin-down time-scale. The results are interpreted in the context of a model for the Earth's fluid core. It is observed that the presence of regions of unstable stratification may increase the decay rate for oscillations at frequencies less than twice the rotation frequency.     

黑河干流中游地区泉水资源衰减原因及趋势分析

根据黑河干流中游地区泉水资源系列资料 (1984～ 1999年 ) ,用布西涅斯克泉水衰减方程和频谱分析方法 ,建立了时间序列预测模型 ,对该地区泉水资源未来变化趋势做了预测 ,结果表明 ,不仅现状处于衰减状态 ,且未来数十年仍继续处于衰减状态。     

Misspecifications in interaction model distance decay relations: A spatial structure effect

 An exclusively statistical approach is proposed to address the spatial structure effects of general interaction models. It is shown that the spatial heterogeneity in the estimated region-specific distance decay parameters may in part be due to the combination of two factors: (a) a functional mis-specification of the global distance decay relationship; and (b) the heterogeneity in the region-specific conditional distance distributions. A properly specified global distance decay function allows controlling for these spatially induced biases in the local distance decay parameters. However, inherent multicollinearities between the set of region specific distance decay parameters and other estimated model parameters prevent an unambiguous interpretation. A key conclusion is that a proper model specification, in particular, the specification of the global distance decay relationship, is of paramount importance in interaction modeling and for accessibility studies. Received: September 2002 / Accepted: January 2003     

关于天然放射性的成因

天然放射性衰变通常被认为是自发性的行为，并且这种衰变有一个恒定的半衰期，尽管有一些实验和经验性的证据对上述基本理论曾提出质疑。许靖华（1994）提出过这方面的问题－衰变作用是否是自发性行为？以及衰变作用是否是粒子与粒子之间相互作用的结果？为了检验β衰变是由中微子与中子相互作用的结果这一论点，对C－14衰变进行实验监测。我们的研究假设，β衰变速率的变化与中微子流的数量之间呈相关关系。在一个短实验周期里，具有较长半衰期的C－14样品的衰变速率应该是一个近似常数。然而我们的实验发现，检测到的衰变速率偏离理论值达1％。这种变化的信号强度超过本底噪声1000倍以上。曾经有一种假说提到，β衰变是由于中子与太阳发出的中微子碰撞产生的，而上述变化与太阳活动无关。经过一年半的实验检测，发现该衰变速率与在北京测量到的宇宙射线强度呈正相关关系。这一结果与作者提出的，β衰变是被宇宙射线的中微子激活的假说相符合。     

一种人口连续分布模型的研究

分析了常用的表示人口分布的方法及其不足，提出了将人口统计数据空间分布化的方法，将研究区域划分为一定分辨率的格网，用距离衰减函数将人口密度估计值分配到每个格网上，每个格网上的人口是均匀分布的，随着格网分辨率的提高，就可以模拟出符合人口说细分布的人口密度空间连续分布模型，并通过实验说明该方法是可行的。     

Atmospheric Turbulence Decay During the Solar Total Eclipse of 11 August 1999

The studies of turbulence decay were based in the past on measurements carried out in neutrally stratified wind tunnels and, more recently, on large-eddy simulation runs. Here the atmospheric turbulence decay process during the solar total eclipse of 11 August 1999 is examined. Thus a rapid transition from convective boundary-layer turbulence to that of a neutral or slightly stable one is considered. A u-v-w propeller anemometer and a fast response temperature sensor located in northern France on top of a 9-m mast recorded the turbulence observations. The measurements, in terms of turbulent kinetic energy decay with time, were found to be in good agreement with those prescribed by a theoretical model of turbulence decay recently proposed. In particular, it was found that the exponent of the power law describing the decay process has the value -2.     

Edge Effect Correction in the S-A Method for Geochemical Anomaly Separation

Anomaly separation using geochemical data often involves operations in the frequency domain, such as filtering and reducing noise/signal ratios. Unfortunately, the abrupt edge truncation of an image along edges and holes (with missing data) often causes frequency distribution distortion in the frequency domain. For example, bright strips are commonly seen in frequency distribution when using a Fourier transform. Such edge effect distortion may affect information extraction results; sometimes severely, depending on the edge abruptness of the image. Traditionally, edge effects are reduced by smoothing the image boundary prior to applying a Fourier transform. Zero-padding is one of the most commonly used smoothing methods. This simple method can reduce the edge effect to some degree but still distorts the image in some cases. Moreover, due to the complexity of geoscience images, which can include irregular shapes and holes with missing data, zero-padding does not always give satisfactory results. This paper proposes the use of decay functions to handle edge effects when extracting information from geoscience images. As an application, this method has been used in a newly developed multifractal method (S-A) for separating geochemical anomalies from background patterns. A geochemical dataset chosen from a mineral district in Nova Scotia, Canada was used to validate the method.