非均匀各向异性弹性波场正演

推导了用于非均匀各向异性弹性波场正演的伪谱法基本公式，对特征值法边界修正方程进行了全面的理论推导，给出了二维和三维问题固体，流体的特征变量及各类边界修正方程，选用2个模型，模拟了2．5维弹性波场，对S波分裂的偏振图像和时间延迟作了较详细的分析。     

An efficient performance‐based seismic design method for reinforced concrete frames

In this paper, a practical method is developed for performance‐based design of RC structures subjected to seismic excitations. More efficient design is obtained by redistributing material from strong to weak parts of a structure until a state of uniform deformation or damage prevails. By applying the design algorithm on 5, 10 and 15‐storey RC frames, the efficiency of the proposed method is initially demonstrated for specific synthetic and real seismic excitations. The results indicate that, for similar structural weight, designed structures experience up to 30% less global damage compared with code‐based design frames. The method is then developed to consider multiple performance objectives and deal with seismic design of RC structures for a design spectrum. The results show that the proposed method is very efficient at controlling performance parameters and improving structural behaviour of RC frames. Copyright © 2011 John Wiley & Sons, Ltd.     

深层地震勘探的地震波传传播理论研究前景

深层地震勘探为地震波传播理论研究提出了新的挑战和机遇。深层地震勘探的主要难点是上覆层的影响甚大，使后续的处理有隔靴挠痒之感，必须应用波场延拓消除上覆层影响。深层波速的高速性和横向不均匀性决定了大角散射和弹性波处理方法的重要性。本文具体评述了深层地震勘探的主要方法对策，深入探讨了波场延拓的李群方法和弹性反演的某些问题，目的在于为深化深层地震提供新的研究手段和方法。     

Thermal behaviour and kinetics of dehydration of gypsum in air from in situ real-time laboratory parallel-beam X-ray powder diffraction

Thermal behaviour and kinetics of dehydration of gypsum in air have been investigated using in situ real-time laboratory parallel-beam X-ray powder diffraction data evaluated by the Rietveld method. Thermal expansion has been analysed from 298 to 373 K. The high-temperature limits for the cell edges and for the cell volume, calculated using the Einstein equation, are 4.29 × 10⁻⁶, 4.94 × 10⁻⁵, 2.97 × 10⁻⁵, and 8.21 × 10⁻⁵. Thermal expansion of gypsum is strongly anisotropic being larger along the b axis mainly due to the weakening of hydrogen bond. Dehydration of gypsum has been investigated in isothermal conditions within the 348–403 K range with a temperature increase of 5 K. Dehydration proceeds through the CaSO₄·2H₂O → CaSO₄·0.5H₂O → γ-CaSO₄ steps. Experimental data have been fitted with the Avrami equation to calculate the empirical activation energy of the process. No change in transformation mechanism has been observed within the analysed temperature range and the corresponding E _a is 109(12) kJ/mol.     

On the stability of a non-convolutional perfectly matched layer for isotropic elastic media

The multi-axial perfectly matched layer (M-PML) is a material boundary condition for wave propagation problems in unbounded domains. It is obtained by extending the formulation of the split-field perfectly matched layer to a more general absorptive medium, for which damping profiles are specified along all dimensions of the problem. Under the hypothesis of small damping, it has been demonstrated that the stability of the system of partial differential equations of the M-PML can be related to the ratio of the damping profiles, and stable M-PML terminations for isotropic and orthotropic elastic media have been constructed. In the present work, we use the Routh–Horwitz determinants to demonstrate that the conclusions regarding the stability of M-PML for isotropic media for small damping are in fact valid for the more general case of damping coefficients of any (positive) value. The effectiveness of the M-PML is demonstrated by constructing stable terminations for the abovementioned media. The stability analysis is presented for 2-D in-plane (P-SV) wave propagation in elastic isotropic continua.     

安徽阜南台家寺遗址出土龟甲的C、N稳定同位素分析

本研究以阜南台家寺遗址出土的商代龟甲及部分动物骨骼为材料,开展了C、N稳定同位素分析,在揭示动物食物结构的基础上初步探讨了先民对龟的使用及龟的来源问题。研究结果显示：龟甲的同位素数据相互之间差异较大,通过聚类分析大致可分为三类：第一类是高δ13C和高δ15N值（δ13C=-20.3 ‰ ±0.4 ‰,n=3;δ15N=7.8 ‰ ±0.2 ‰,n=3）;第二类是δ13C值居中,δ15N值偏低（δ13C=-21.6 ‰ ±0.4 ‰,n=4;δ15N=7.0 ‰ ±0.3 ‰,n=4）;第三类是δ13C值偏低、δ15N值居中（δ13C=-23.7 ‰ ±0.6 ‰,n=4;δ15N=7.6 ‰ ±0.3 ‰,n=4）,这意味着该遗址出土的龟甲可能存在多种来源。究其原因,可能缘于先民制作卜甲时使用的龟来源于不同的栖息环境,抑或来源于不同种属的龟。这种用龟行为,或许与殷墟甲骨上记载的"贡龟"密切相关。尽管本研究通过稳定同位素分析揭示商代先民的用龟行为尚属初步,但毋庸置疑,本研究为全面探索商代先民的用龟行为、拓展甲骨学的研究领域提供了新的研究证据和视角。     

基于简化的Pride理论模拟声电效应测井响应

针对声电效应测井问题，提出了一种全波列数值模拟方法.该方法忽略声电效应测井 时转换电场对声场的影响,并将电场视为似稳场.采用点声源模型，依据Biot理论得出了井外 孔隙介质声场的表达式，运用这些表达式和似稳电场近似方法，导出了声电效应测井时转换 电场的计算公式.在计算出的转换电场波形中，有伴随斯通利波的电场、伴随纵波和横波的 电场、和临界折射电磁波场.在25kHz以下的频率范围内，依据这种方法计算出来的声电转换 波波形与依据完整Pride理论计算的波形一致.     

弹性各向同性介质一次散射波场高斯束Born正演

本文提出了一种弹性波一次散射波场的正演方法——弹性波高斯束Born正演.该方法以线性散射理论为基础,通过Born近似建立起地下散射点处不同波型的反射率同弹性波主分量波场之间的数据映射关系,利用高斯束所包含的走时、振幅和极性信息进行不同波型的局部平面波的合成,进而通过逆倾斜叠加将所合成的局部平面波转化为时空域的多分量地震记录.该方法不但保持了射线类方法高效的优点,还具备了处理多次走时波场的能力,从而保证了复杂构造的波场模拟的精度.文中两个数值模型的应用效果表明,本文所提出的弹性波高斯束Born正演算法具有近似于波动方程有限差分法的波场模拟精度以及高得多的计算效率.

     

Characterizing the effect of elastic interactions on the effective elastic properties of porous,cracked rocks

Elastic interactions between pores and cracks reflect how they are organized or spatially distributed in porous rocks. The principle goal of this paper is to understand and characterize the effect of elastic interactions on the effective elastic properties. We perform finite element modelling to quantitatively study how the spatial arrangement of inclusions affects stress distribution and the resulting overall elasticity. It is found that the stress field can be significantly altered by elastic interactions. Compared with a non‐interacting situation, stress shielding considerably stiffens the effective media, while stress amplification appreciably reduces the effective elasticity. We also demonstrate that the T‐matrix approach, which takes into account the ellipsoid distribution of pores or cracks, can successfully characterize the competing effects between stress shielding and stress amplification. Numerical results suggest that, when the concentrations of cracks increase beyond the dilute limit, the single parameter crack density is not sufficient to characterize the contribution of the cracks to the effective elasticity. In order to obtain more reliable and accurate predictions for the effective elastic responses and seismic anisotropies, the spatial distribution of pores and cracks should be included. Additionally, such elastic interaction effects are also dependent on both the pore shapes and the fluid infill.     

无限饱水孔隙弹性空间中由运动源所产生的位移场

基于Ｂｉｏｔ的饱和孔隙弹性介质的运动方程和利用复变函数方法，本文研究了无限饱水孔隙弹性空间中由常速运动源所产生的位移场。考虑了两种类型源：ａ．沿无限空间水平轴运动的斜向集中力源；ｂ．运动双力偶源。关于力源的运动速度，考虑了４种情形：ａ．力源的运动速度Ｕ小于饱水孔隙弹性介质的三种体波速度一亚音速情形；ｂ．速度Ｕ小于介质的第一纵波过度和横波速度，但大于第二纵波速度─—弱跨音速情形；ｃ．速度Ｕ小于第一纵波速度，但大于横波速度和第二级波速度─—强跨音速情形；ｄ．速度Ｕ大于介质的所有三种体波速度─—超音速情形。结果表明，在跨音达和超音速情形里，解呈现出与力源相联系的平面冲击波特征，位移出现了相应的跳跃。