一次强降水系统的演变和细结构分析

文章分析1992年7月23日河北省东部平原地区一次突发性暴雨过程，研究了产生特大暴雨的中-α尺度对流系统的演变及其细结构，讨论了该系统内部中心暖区形成的物理机制，并指出几种不同尺度的天气系统相互作用对这次暴雨系统的重要影响。     

Radiation-induced defects in quartz. II. Single-crystal W-band EPR study of a natural citrine quartz

Single-crystal electron paramagnetic resonance (EPR) spectra of a natural citrine quartz without any artificial irradiation, measured at W-band frequencies (∼94 GHz) and temperatures of 77, 110 and 298 K, allow better characterization of three previously-reported Centers (#6, #7 and B) and discovery of three new defects (B′, C′ and G′). The W-band EPR spectra reveal that Centers #6 and #7 do not reside on twofold symmetry axes, contrary to results from a previous X-band EPR study. The W-band spectra also show that the previously reported Center B is a mixture of two defects (B and B′) with similar g matrices but different-sized ²⁷Al hyperfine structures. Center C′ has similar principal g values to the previously reported Center C but is distinct from the latter by a larger ²⁷Al hyperfine structure with splittings from 0.10 to 0.22 mT. Also, Center G′ has a similar g matrix to the previously reported Center G but a different ²⁷Al hyperfine structure with splittings from 0.41 to 0.53 mT. These spin-Hamiltonian parameters, together with observed thermal properties and microwave-power dependence, suggest that Centers #6 and #7 probably represent O₂³⁻ type defects. Centers B and B′ are probably superoxide radicals (O₂⁻) with the unpaired spin localized on the same pair of oxygen atoms around a missing Si atom but linked to a substitutional Al³⁺ ion each at different neighboring tetrahedral sites. Similarly, Centers G and G′ are most likely superoxide radicals with the unpaired spin localized on another pair of oxygen atoms around a missing Si atom and linked to a substitutional Al³⁺ ion each at different neighboring tetrahedral sites. Center C′ is probably an ozonide radical associated with a missing Si atom and linked to a substitutional Al³⁺ ion at the neighboring tetrahedral site. This study exemplifies the value of  high-frequency EPR for discrimination of  similar defect centers and determination of  small local structural distortions that are often difficult to resolve in conventional  X- and Q-band EPR studies.     

Elastic wave mode separation for tilted transverse isotropy media

Seismic waves propagate through the earth as a superposition of different wave modes. Seismic imaging in areas characterized by complex geology requires techniques based on accurate reconstruction of the seismic wavefields. A crucial component of the methods in this category, collectively known as wave‐equation migration, is the imaging condition that extracts information about the discontinuities of physical properties from the reconstructed wavefields at every location in space. Conventional acoustic migration techniques image a scalar wavefield representing the P‐wave mode, in contrast to elastic migration techniques, which image a vector wavefield representing both the P‐ and S‐waves. For elastic imaging, it is desirable that the reconstructed vector fields are decomposed into pure wave modes, such that the imaging condition produces interpretable images, characterizing, for example, PP or PS reflectivity. In anisotropic media, wave mode separation can be achieved by projection of the reconstructed vector fields on the polarization vectors characterizing various wave modes. For heterogeneous media, because polarization directions change with position, wave mode separation needs to be implemented using space‐domain filters. For transversely isotropic media with a tilted symmetry axis, the polarization vectors depend on the elastic material parameters, including the tilt angles. Using these parameters, we separate the wave modes by constructing nine filters corresponding to the nine Cartesian components of the three polarization directions at every grid point. Since the S polarization vectors in transverse isotropic media are not defined in the singular directions, e.g., along the symmetry axes, we construct these vectors by exploiting the orthogonality between the SV and SH polarization vectors, as well as their orthogonality with the P polarization vector. This procedure allows one to separate all three modes, with better preserved P‐wave amplitudes than S‐wave amplitudes. Realistic synthetic examples show that this wave mode separation is effective for both 2D and 3D models with strong heterogeneity and anisotropy.     

滇西及缅甸Ms≥6．8级地震时空对称性研究

灾害趋势判断是提高灾害预测预报水平的重要途径。根据1950年以来滇西地区和缅句Ms≥6．8级地震资料,通过三元、四元、五元可公度法计算、蝴蝶结构图和可公度结构系分析,对该地区地震灾害的时间对称性进行了趋势判断。理论计算结果表明：该研究区域2014和2016年强震信号较强,有可能发生较大震级地震。根据空间对称性和强震震中经、纬向迁移特征分析,判断出下一次地震发生地点大致在97．5°E以西,22．5°N以南地区。该研究可丰富重大灾害趋势判断研究案例。     

Fabric symmetry of low anisotropic rocks inferred from ultrasonic sounding: Implications for the geomechanical models

The geomechanical models were established based on the absence or presence of certain rock fabric elements — texture (crystallographic preferred orientation), microstructure (shape preferred orientation) and microcracks (flat voids). The proposed models include both (i) the ideal material showing random texture and structure but no microcracks, i.e. the material which is hardly to be found in nature, and (ii) the materials possessing various combinations of fabric elements that show different spatial arrangements. The mutual relationship between those parameters and seismic and geomechanical properties are discussed.Selected models were experimentally verified during laboratory experiments. These consist of measurement of P-wave velocities in 132 independent directions under several confining pressures in the range 0.1–400 MPa. From measured data 3D P-wave patterns can be constructed and the influence of microcracks and of texture and structure on the rock seismic anisotropy can be determined. The seismic anisotropy established at different levels of confining pressure can be used for the interpretation of rock fabric symmetry of rocks showing low anisotropy in macroscale and for the selection of directions in which the geomechanical test can be performed. The measured P-wave velocities were then mathematically processed by using a fitting function which reflects contribution of P-wave velocity in the mineral skeleton of an ideal sample without microcracks extrapolated to the atmospheric pressure level from high confining pressure interval (ca. 200–400 MPa) (v₀), linear compressibility of the samples (k_v), and confining pressure during which most of the cracks are closed (P₀). These parameters improve the understanding of the response of various rock fabric elements on increasing confinement and corresponding changes in elasticity.The observed seismic and geomechanical anisotropies reflect intensity of the fabric of rock-forming minerals and microcracks. The magnitude of seismic anisotropy measured at atmospheric pressure corresponds to the anisotropy of static elastic modulus and is governed by the spatial arrangement of microcracks. The magnitude of strength anisotropy (uniaxial compressive strength) correlates more likely to the seismic anisotropy determined at high confining pressure and is connected to the preferred orientations (either CPO or SPO or both) of rock-forming minerals.     

对称点群操作和对称操作变换矩阵

在结晶学和晶体结构测定中,由于计算上的某种需要,常常把原来的坐标系以原点为中心,按照某种方式转动某一角度而成为一种新坐标系。由于新、老坐标系有共同的原点,因此它们之间必然存在着某种内在上的联系,也就是说它们中的一种坐标系的某些量可以用另一个坐标的某些量的数学式来表示。坐标系变换后,结晶学中的一系列指数,如点群,晶面指数(hkl),晶棱方向指数[uvw],倒易点阵矢量等都会跟着变换。本文试图从数学出发,揭示这种变换关系,即变换矩阵。     

城市系统的异速生长关系与位序-规模法则——对Steindl模型的修正与发展

基于Steindl模型的建模思想，设置一个时间－年龄变量T，将城市规模（P）－数目（f)异速生长的假设条件重新构造为dP(T)/dT=gP(T),df(T)/dT=-rf(T)，据此导出反映城市等级－规模关系的Beckmann-Davis模型：P（m)-P1λ^m-1,f(m)=f1δ^1-m，进而导出三参数Zipf定律：P（r)=C(r-a)^-dx,式中g=lnλ，r=lnδ,C=p1[δ/(δ-1)]^dx，α=1/(1-δ),dz=g/r=lnλ/lnδ。根据几何测度关系建立分维方程：dz=Dp/Df，从而揭示：城市规模分布的分维D＝1／dz在本质上乃是城市体系空间结构的分维Df与各城市人口空间分布的平均维数Dp之比。     

二维大气中定常广义地转流的稳定性分析

本文归纳总结了在绝热、无耗散对称二维大气中定常广义地转流稳定性分析中的扰动方程组的基本特征，并将其概括为具有这类问题共同基本特征的统一形式的扰动方程组的定解问题。在此基础上，统一地证明了：１）由统一的扰动方程组所确定的定解问题的解是存在唯一的；２）基态的性质是由Λｍｉｎ（Ｇ）的性质决定的：ａ．当Λｍｉｎ（Ｇ）＞０时，基态是稳定的；ｂ．当Λｍｉｎ（Ｇ）＜０时，基态是不稳定的。３）基态的全局稳定性质可以通过局部稳定性分析来确定；４）合理的、充分简化的局部稳定性分析结论在局部分析中是严格有效的     

Radiation-damage-induced defects in quartz. I. Single-crystal W-band EPR study of hole centers in an electron-irradiated quartz

Single-crystal W-band electron paramagnetic resonance (EPR) spectra of an electron-irradiated quartz, measured at room temperature, 110 and 77 K, disclose three previously reported hole centers (#1, G and an ozonide radical). The W-band EPR spectra of these three centers clearly resolve six magnetically nonequivalent sites each, whereas previous X- and Q-band EPR studies reported Centers #1 and the ozonide radical to consist of only three symmetry-related components and interpreted them to reside on twofold symmetry axes in the quartz structure. The calculated g matrices of Center #1 and the ozonide radical show that deviations from twofold symmetry axes are <10°, which are probably attributable to distortion related to neighboring charge compensating ions. The W-band EPR spectra of Center G not only result in improved g matrices but also allow quantitative determination of the nuclear hyperfine (A) and quadrupole (P) matrices of its ²⁷Al hyperfine structure that was incompletely resolved before. In particular, the g-maximum and g-minimum principal axes of Center G are approximately along two pairs of O–O edges of the SiO₄ tetrahedron, while the unique A principal axis is approximately along a Si–Si direction. These new spin-Hamiltonian parameters suggest that Center G most likely involves trapping of a hole between two oxygen atoms related to a silicon vacancy and stabilized by an Al³⁺ ion in the neighboring tetrahedron (hence an O₂ⁿ⁻–Al³⁺ defect, where n is either 1 or 3).     

周期基数插值尺度函数和小波函数的对称性

设 g(x1,x2 )是一个 Fourier系数为正的周期函数 ,研究了二维周期基数插值小波函数。得到了关于 g(x1,x2 )的二维周期基数插值的尺度函数和小波函数的对称性