Simple analytical Green's functions for ray perturbations in layered media

The total Green's function for two-point boundary-value problems can be related to the propagator for initial-value problems. A very simple expression for the Green's function is obtained when the unperturbed medium may be described by material with a constant gradient in quadratic slowness. The derivation requires a correct understanding of assumptions made in the propagator solution. Expressions are also obtained for Green's function in multilayered media.     

东南亚夏季风中断、过渡与活跃期的区域能量学研究

对两次季风演变过程的能量学研究表明，季风演变具有鲜明的阶段性能量学特征。中断期，积云加热小，两个转换函数值很小；过渡期，积云加热增强明显，两个转换函数值迅速加大，边界输送作用也明显朝有利方向变化，同时，纬向平均气流变为向季风供应扰动动能；活跃期，大尺度加热变得重要，积云加热维持，两个转换函数也保持大的正值。分析表明，印度季风东传对东南亚季风活跃的触发作用是重要的，但季风活跃的维持则主要依靠区域内部能量学过程。     

The Relegation Algorithm

The relegation algorithm extends the method of normalization by Lie transformations. Given a Hamiltonian that is a power series = ₀+ ₁+ ... of a small parameter , normalization constructs a map which converts the principal part ₀into an integral of the transformed system — relegation does the same for an arbitrary function [G]. If the Lie derivative induced by [G] is semi-simple, a double recursion produces the generator of the relegating transformation. The relegation algorithm is illustrated with an elementary example borrowed from galactic dynamics; the exercise serves as a standard against which to test software implementations. Relegation is also applied to the more substantial example of a Keplerian system perturbed by radiation pressure emanating from a rotating source.This revised version was published online in October 2005 with corrections to the Cover Date.     

The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations

GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004) were created. The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the response of TEC to the storm for European and North American sectors are analyzed.     

用变分法修正黑河试验数据的初步研究

为了对黑河试验观测资料进行订正,利用一个一维边界层垂直扩散模式和以拟牛顿极小化算法为基础的最优化方法建立了一个变分同化系统,其中,目标函数相对于控制变量的梯度用扰动法求取.并利用模式资料和黑河试验若干时刻的观测资料进行了一些数值试验.试验证明,将初始场变量与模式误差系数同时作为控制变量加以调整,能够有效调整初始场观测资料.并且,用变分同化方法能够较线性插值(时间、空间)方法更有效、合理的修正黑河试验观测资料场的种种缺陷.     

金属矿地震散射波场的数值模拟研究

地震方法用于寻找石油、煤田等沉积层控矿床已取得许多成功经验和大量的成果；对于金属矿可依据微扰理论，通过地震波散射响应的强弱推断矿体。模拟实验结果表明，散射波相干性的好坏与杂乱散射体的不均匀性有关；不均匀性越强，产生的散射相干性就越好。     

边坡稳定可靠性的随机有限元分析

随机有限元法可以处理土性参数的变异性和空间相关性。对二阶摄动随机有限元法的摄动理论和程序进行了研究，提出了偏导矩阵的组集方法，采用正态分布随机变量的正交变换法来提高计算效率。考虑土性参数随机场作用和土性指标之间的互相关性，建立边坡局部抗剪和总体稳定性可靠度的随机有限元分析模型，对某实际土坡进行了可靠度计算，计算结果较为符合实际。     

Upscaling Uncertain Permeability Using Small Cell Renormalization

Sedimentary rocks have structures on all length scales from the millimeter to the kilometer. These structures are generally associated with variations in rock permeability. These need to be modeled if we are to make predictions about fluid flow through the rock. However, existing computers are not powerful enough for us to be able to represent all scales of heterogeneity explicitly in our fluid flow models—hence, we need to upscale. Small cell renormalization is a fast method for upscaling permeability, derived from an analogue circuit of resistors. However, it assumes that the small scale permeability distribution is known. In practice, this is unlikely. The only information available about small scale properties is either qualitative, derived from the depositional setting of the reservoir, or local to the wells as a result of coring or logging. The influence of small scale uncertainty on large scale properties is usually modelled by the Monte Carlo method. This is time-consuming and inaccurate if not enough realisations are used. This paper describes a new implementation of renormalization, which enables the direct upscaling of uncertain small-scale permeabilities to produce the statistical properties of the equivalent coarse grid. This is achieved by using a perturbation expansion of the resistor-derived equation. The method is verified by comparison with numerical simulations using the Monte Carlo method. The prediction of expected large-scale permeability and its standard deviation are shown to be accurate for small cell standard deviations of up to 40% of the mean cell value, using just the first nonzero term of the perturbation expansion. Inclusion of higher order terms allows larger standard deviations to be modeled accurately. Evaluation of cross-terms allows correlations of actual cell values, over and above the background structure of mean cell values. The perturbation method is significantly faster than conventional Monte Carlo simulation. It needs just two calculations whereas the Monte Carlo method needs many thousands of realisations to be generated and renormalized to converge. This results in significant savings in computer time.     

地面总辐射的异常减少对气候影响的数值试验

在与实际台风场近似一致的环境流场条件下，应用柱会标中的正压无辐散模式，讨论了台风中扰动的稳定性问题。研究表明，台风暖心结构的台风外围适当强度的冷空气活动有利限台风中扰动发展，且台风愈强，台风中扰动愈易发展。