网红城市网络关注度时空动态演变及影响因素研究——以西安市为例

基于媒介地理学,以网红西安为切入点,结合数理统计、空间分析和地理探测器等方法,选取百度指数2017—2019年中国361个市域对西安市的网络关注度数据,分析网红西安虚拟空间建构的时空动态演变和影响因素。研究发现：① 时间上,2017—2019年西安市的网络关注度持续上升,季节差异显著,月际变化表现出明显的“前兆效应”。② 空间上,胡焕庸线以东区域的西安市网络关注度高于界线以西区域,区域差异逐渐缩小,东部省（市、自治区）大多为高关注度区,省会城市普遍高于该省其他城市,且西安市网络关注度显著热点区和显著冷点区连片分布,次热点区围绕显著热点区分布。③ 影响因素上,气候舒适度、闲暇时间及网红形象符号是影响西安市网络关注度时间分布的主要因素,客源地互联网发达程度、年龄结构、GDP规模、常住人口、受教育程度及两地的地理空间距离是影响空间分布的重要因素,其它因素影响力较弱。可见,媒介通过日常生活中城市居民的空间实践,重构了城市形象,同时也形塑了“人–媒介–城市”互动的动态虚拟空间,成为现代城市空间生产及实践重要构成要素。     

双相介质瑞雷面波有限差分正演模拟

为了研究双相介质瑞雷面波的形成机制及传播规律,促进瑞雷面波资料处理方法的发展。文章根据弹性波动方程,采用交错网格有限差分算法,对二维各向同性弹性介质做解析解与数值解的对比,在此基础上,将PML吸收边界条件,改进的镜像法应用于双相介质波动方程中,并作了稳定性分析,对双相介质水平层状、起伏分界面等典型模型瑞雷面波及体波在内的全波场进行研究。结果表明:基于弹性介质解析解与数值解的对比,在误差接受范围内,研究双相介质是可行的;把稍作改进的镜像法应用于双相介质中,能够有效地处理瑞雷面波自由边界问题;通过详细分析双相介质瑞雷面波及体波在内的全波场的信息,对以双相介质为基础的地震波勘探有一定的指导作用。     

基于能量守恒方法的重力场反演快速异构并行算法

在利用卫星跟踪卫星资料解算重力场模型位系数时,其海量观测数据处理以及大型方程组解算过程存在计算效率低下、对平台硬件要求高等问题。针对以上问题,提出一种基于能量守恒方法的重力场反演快速异构并行算法,基于CUDA 在GPU端实现并行计算设计矩阵,结合MKL库与分区平差法、预处理共轭梯度法在CPU端完成低内存消耗下的法方程快速构建与求解,实现重力场模型反演的异构并行计算。运用该算法处理GRACE-FO卫星2020-01-01～06-30期间观测数据,反演获得120阶重力场模型GM-GraceFO2020h;与现有模型以及算法对比分析表明,该算法所得模型与现有GRACE重力场模型精度相当,且相较于传统的串行算法,反演耗时减少98.479%,内存消耗减小1个数量级。     

含水层的一种普遍规律:渗透系数随深度衰减

国内外多个含水层的研究都发现渗透系数具有随深度衰减的规律。给出了多孔介质和裂隙介质中渗透系数随深度衰减的一般模型及简化模型,并用该简化模型分析了多个含水层的渗透系数随深度衰减的规律。研究发现,随着渗透系数测试深度的增大,衰减系数明显变小;渗透系数测试深度相近的含水层,岩性对衰减系数有一定程度影响。渗透系数随深度衰减的规律应该在地下水科学的相关研究中引起重视。     

Uniform asymptotic Green's functions for efficient modeling of cracks in elastic layers with relative shear deformation controlled by linear springs

We present a uniform asymptotic solution (UAS) for a displacement discontinuity (DD) that lies within the middle layer of a three‐layer elastic medium in which relative shear deformation between parallel interfaces is controlled by linear springs. The DD is assumed to be normal to the two interfaces between the elastic media. Using the Fourier transform method we construct a leading term in the asymptotic expansion for the spectral coefficient functions for a DD in a three‐layer‐spring medium. Although a closed‐form solution will require a solution in terms of an infinite series, we demonstrate how this UAS can be used to construct highly efficient and accurate solutions even in the case in which the DD actually touches the interface. We compare the results using the Green's function UAS solution for a crack crossing a soft interface with results obtained using a multi‐layer boundary element method. We also present results from an implementation of the UAS Green's function approach in a pseudo‐3D hydraulic fracturing simulator to analyze the effect of interface shear deformation on the fracture propagation process. These results are compared with field measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

An anisotropic damage–plasticity model for saturated quasi‐brittle materials

This article is devoted to numerical modeling of anisotropic damage and plasticity in saturated quasi‐brittle materials such as rocks and concrete. The damaged materials are represented by an isotropic poroelastic matrix containing a number of families of microcracks. Based on previous works, a discrete thermodynamic approach is proposed. Each family of microcracks exhibits frictional sliding along crack surfaces as well as crack propagation. The frictional sliding is described by a Coulomb–Mohr‐type plastic criterion by taking into account the effect of fluid pressure through a generalized effective stress concept. The damage evolution is entirely controlled by and coupled with the frictional sliding. The effective elastic properties as well as Biot's coefficients of cracked porous materials are determined as functions of induced damage. The inelastic deformation due to frictional sliding is also taken into account. The procedure for the identification of the model's parameters is presented. The proposed model is finally applied to study both mechanical and poromechanical responses of a typical porous brittle rock in drained and undrained compression tests as well as in interstitial pressure controlled tests. The main features of material behaviors are well reproduced by the model. Copyright © 2012 John Wiley & Sons, Ltd.     

Solid–liquid–air coupling in multiphase porous media

This paper addresses various issues concerning the modelling of solid–liquid–air coupling in multiphase porous media with an application to unsaturated soils. General considerations based on thermodynamics permit the derivation and discussion of the general form of field equations; two cases are considered: a three phase porous material with solid, liquid and gas, and a two phase porous material with solid, liquid and empty space. Emphasis is placed on the presentation of differences in the formulation and on the role of the gas phase. The finite element method is used for the discrete approximation of the partial differential equations governing the problem. The two formulations are then analysed with respect to a documented drainage experiment carried out by the authors. The merits and shortcomings of the two approaches are shown. Copyright © 2003 John Wiley & Sons, Ltd.     

Response of saturated porous media to cyclic thermal loading

The response of a semi‐infinite saturated porous medium subjected to a harmonic thermal loading on its free face is studied herein. The pressure diffusion equation that governs the fluctuation of the interstitial pressure is established. It allows us to obtain prevalent parameters, i.e. the thermal and fluid mass diffusivities and the coefficient of relative bulk variation. Closed‐form solutions of the maximum fluid pressure P_max and its location x_cr are derived. It is shown that the location x_cr of P_max is localized and depends on the diffusivity ratio and the frequency of the thermal loading while the magnitude of P_max depends on the diffusivity ratio and the thermal amplitude. Master curves for x_cr and P_max versus diffusivity ratio are built. It follows that three regimes can be distinguished: namely, thin spalling, thick spalling or in‐depth cracking and no cracking. Copyright © 2003 John Wiley & Sons, Ltd.     

气象远程教育流媒体课件录制系统的开发和应用

网络教育的高速发展,使网络课件成为课件制作系统的发展方向,而且开发一个和网络教学系统高度集成的课件制作系统也成为必然的趋势。中国气象局培训中心内蒙古气象远程教育二级站已于2007年年初落成并投入使用。硬件设备已达到建设标准,软环境还处于空白。因此,急需投入一定的人力和财力进一步开发与硬件相适应的课件录制和课件点播系统。这对于我区气象系统远程教育的发展十分必要。