An Interactive Sampling Strategy Based on Information Analysis and Ordinary Kriging for Locating Hot Spot Regions

This study proposes an interactive sampling strategy for locating the hot spot or maximum regions of a concerned attribute in a given area of survey. In the proposed strategy, information analysis is performed based on the ordinary kriging from the existing sample data to suggest a new batch of samples under the criterion of the highest information free energy. The information free energy (F) is a function of information energy (U) and information entropy (S) through F = U - TS, where T is information temperature and is used to coordinate the contribution of U and S to F. Information energy is the value of the concerned attribute, and information entropy is the transformed error variance of kriging and therefore measures the evenness and density of coverage of samples over the area under survey. At early sampling batches, information temperature is high and information entropy dominates the information free energy, and samples are suggested to give an even and dense enough coverage of the whole area under investigation. As samples accumulate, information temperature decreases to enlarge the contribution of information energy, and future samples are taken toward the locations with high attribute values. Two examples demonstrate the efficiency and effectiveness of the proposed sampling strategy in locating the hot spot regions of various fields: (1) a heavy metal contaminated site reproduced by modeling on 55 real field data; (2) a simulated two-dimensional field by the random phase volume (RPV) model. The results show that the proposed strategy, a robust interactive sampling procedure, is able to locate hot spot regions without compromising with the overall profile of an under-survey area.     

一次逼近理论下边坡稳定的模糊随机数值分析

在协调元基础上,通过一次逼近理论,建立随机有限元模型,并通过模糊数学模型实现对边坡体工作状态的软化处理;借助于模糊随机数值方法对荆南长江干堤局部破坏失效进行了较为全面的研究。     

A study of the chemistry of pore fluids and authigenic carbonates in methane seep environments: Kodiak Trench, Hydrate Ridge, Monterey Bay, and Eel River Basin

Analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the Kodiak Trench, Hydrate Ridge, Monterey Bay Clam Flats, and the Eel River Basin, coupled with the studies of the chemistry of the pore fluids, have shown that these carbonates have grown within the sediment column. Geochemical profiles of pore fluids show that, in deep water seeps (Kodiak Trench—4450 m; Monterey Bay—1000 m; Hydrate Ridge—650 m), δ¹³C (DIC) values are low (isotopically light), whereas in the Eel River area ( 350–500 m), δ¹³C (DIC) values are much higher (isotopically heavier). In all cases, the δ¹³C values indicate that processes of methane oxidation, associated with sulfate reduction, are dominant in the shallow sediments. Data on the isotopic composition of authigenic carbonates found at sites in Kodiak Trench, Eel River Basin South, and Eel River Basin North indicate a variable composition and origin in different geochemical environments. Some of the authigenic carbonates from the study sites show a trend in their δ¹³C values similar to those of the pore fluids obtained in their vicinity, suggesting formation at relatively shallow depths, but others indicate formation at greater sediment depths. The latter usually consist of high magnesium calcite or dolomite, which, from their high values of δ¹³C (up to 23‰;) and δ¹⁸O (up to 7.5‰), suggest formation in the deeper horizons of the sediments, in the zone of methanogenesis. These observations are in agreement with observations by other workers at Hydrate Ridge, in Monterey Bay, and in the Eel River Basin.     

The structure of SrTiOGeO4 and its solid solution with CaTiOGeO4

Solid solubility and structural phase transitions in (Ca _x Sr_1-x )TiOGeO₄have been studied by means of in situ high temperature X-ray powder diffraction. The displacive A2/a–P2₁/a phase transition analogous to titanite has been followed across the solid solution. Strain analysis indicates a transition temperature of T _c=594 ± 10 K for SrTiOGeO₄ and the additional occurrence of an isosymmetric anomaly at T _i =800 ± 25 K, in analogy to the isomorphous compound CaTiOGeO₄. Lattice parameters as a function of temperature and composition have been determined by X-ray powder diffraction between room temperature and a maximum temperature of 1123 K. The e ₁₁ and e ₁₃ components dominate the strain tensor. All compositions across the solid solution exhibit close to tricritical phase transitions P2₁/a–A2/a. The critical temperature remains almost unaffected by substitution of Sr for Ca, but the magnitude of the spontaneous strain drops significantly with even small amounts of Sr present.     

探地雷达复信号分析的几点讨论

采用H ilbert变换的复信号分析方法,求取相位时对噪声很敏感,所以分析前的滤波处理是非常重要的,常用的反正切求取相位角方法,不利于求取包含真实反射信息的相位θ(t)。针对以上两个问题,采用了与探地雷达垂向分辨能力相关的尺度,对原始数据进行了滤波操作。滤波后的数据保证了与原始数据相同的分辨能力,有效地压制了干扰信号。同时,具有良好的数学性质,为复信号分析提供了有利的条件。利用反余弦计算相角,方便了程序设计,且求得的相角易于变换为真实相角(ω0t θ(t)),为提取真正与反射信息相关的相位θ(t)提供了便利。应用优化方法求解瞬时相位、瞬时频率等信息,将真正与反射信息相关的θ(t)与ω0t分离,提高了分辨能力,同时还可得到ω0随时间变化的曲线,为分析探地雷达的频散现象提供了依据。     

电吸附找矿法在捕获常规化探方法难以发现的异常时的有效性

电吸附找矿法是一种针对寻找隐伏矿而研制的找矿新方法，它属金属活动态提取法的一种，其找矿原理是：深埋藏隐伏矿在地电化学作用下发生溶解，溶解出来的矿物质在各种迁移动力的驱动下，从地下深部向上运移到地表，进入土壤形成后生异常。后生异常组分多属活动态，但活动态组分不仅存在于后生异常中，也存在于同生异常——原生晕异常和次生晕异常中，因此，应用电吸附找矿法寻找露头矿和浅埋藏矿时，其效果与常规化探方法是一样的；但电吸附找矿法的主要作用是可应用于寻找深埋藏隐伏矿，因由隐伏矿引起的后生异常活动态组分含量很低，常规化探方法很难发现它，而电吸附找矿法却能捕获它。     

Gravity change and its mechanism after the first water impoundment in Three Gorges Project

Introduction During and before the construction of the Three Gorges Project, the annual observation was continuously undertaken by the Three Gorges gravity observation network established around the head area of the reservoir (the section between Sandouping and Badong). This network has pro-vided substantial high precise data related to seismic activity. However, the annual gravity survey together monitoring of the existed observation stations can hardly effective monitor some potential sei…     

Wave velocities in a pre-stressed anisotropic elastic medium

Modified Christoffel equations are derived for three-dimensional wave propagation in a general anisotropic medium under initial stress. The three roots of a cubic equation define the phase velocities of three quasi-waves in the medium. Analytical expressions are used to calculate the directional derivatives of phase velocities. These derivatives are, further, used to calculate the group velocities and ray directions of the three quasi-waves in a pre-stressed anisotropic medium. Effect of initial stress on wave propagation is observed through the deviations in phase velocity, group velocity and ray direction for each of the quasi-waves. The variations of these deviations with the phase direction are plotted for a numerical model of general anisotropic medium with triclinic/ monoclinic/orthorhombic symmetry     

Pseudo-dynamic approach of seismic active earth pressure behind retaining wall

Knowledge of seismic active earth pressure behind rigid retaining wall is very important in the design of retaining wall in earthquake prone region. Commonly used Mononobe-Okabe method considers pseudo-static approach, which gives the linear distribution of seismic earth pressure in an approximate way. In this paper, the pseudo-dynamic method is used to compute the distribution of seismic active earth pressure on a rigid retaining wall supporting cohesionless backfill in more realistic manner by considering time and phase difference within the backfill. Planar rupture surface is considered in the analysis. Effects of a wide range of parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity and horizontal and vertical seismic accelerations on seismic active earth pressure have been studied. Results are provided in tabular and graphical non-dimensional form with a comparison to pseudo-static method to highlight the realistic non-linearity of seismic active earth pressures distribution.     

用低通滤波器探测和修复单频GPS载波相位的周跳

使用一种在时间序列分析中常用的异常值的检测方法双低通滤波器奇异值检定法来检测GPS载波相位观测值中的周跳，给出了数据窗的宽度Vmax以及门槛系数女，提出了利用低通滤波器进行周跳定值的迭代计算方法。试验表明，该方法计算简单，能够探测1周甚至0．5周的周跳。