Effects of underground cavities on Rayleigh waves—Field and numerical experiments

This paper presents the results of a multi-channel analysis of surface waves (MASW) test conducted over near-surface mine workings, with the objective of delineating the underlying. Numerical studies were carried out to explain and extend the results. The displacement time histories at the surface show amplitude changes in the region over the void, and the Fourier spectra show significant energy concentration on and in the vicinity of the cavity. Different numerical models are constructed and the responses at the surface of the medium and around voids of different sizes and embedment depths are monitored. The numerical results show that part of the incident energy is trapped within the void. The trapped energy bounces back and forth inside the void, until it is attenuated by radiation. The effect of the trapped energy is seen as a concentration of energy over the void region in the frequency domain. The amount of trapped energy is a function of the size and embedment of the void, as well as of the frequency content of the source. The void absorbs part of the energy and radiates it as body waves. Therefore, the recorded responses at the surface carry valuable information about the void. The characteristics of the void can be extracted from the surface responses by analyzing the responses in time, frequency, and spatial domains.     

ulti-azimuth three-component surface seismic modeling for viscoelastic cracked monoclinic media

针对粘弹性裂隙型单斜介质,本文应用高阶交错网格差分法,对其传播快照以及多方位地面三分量记录进行模拟,结果证明了裂隙填充物的性质引起的各向异性与粘弹性性质对单斜介质波场有明显的影响,总结了不同观测方位地震记录呈现出的规律性,这为进一步了解波场在介质中的传播情况,提出更合理的理论模型,提供一种尝试.     

Urban land expansion and arable land loss of the major cities in China in the 1990s

China is a country with vast population and scarce arable land per capita. China’s population is more than 1.2 billion, about one-fifth of the world’s total, while the arable land area is only 0.106 hm2 per capita, less than half of the world’s average of 0.23 hm2[1]. Arable land conservation/food security has been acknowl- edged as one of the main factors affecting the sustain- able socio-economic development in China[2], which catches the special attention of many scholars at home and abr…     

四川省巫山县两个村的贫富差距

1979年后,城镇经济的辐射,交通运输的发展,激发了兴胜人的致富动机,75％的农民成为多重职业者,人的素质及经营能力得到提高。这是兴胜脱贫致富的重要原因。庙堂这样的贫困村要脱贫致富,一是依靠政策;三是依靠科技;三是依靠投入,以便改善自然-社会环境;四是依靠服务。在开发资源、发展经济的过程中,提高人的素质和经营能力,落后村庄的脱贫致富是有望的。     

深基坑降水疏干过程中三维渗流场数值模拟研究

运用潜水、承压水渗流理论和有限差分法,以及干湿单元、预处理共扼梯度算法,以上海环球金融中心塔楼深基坑降水为依托工程,对深基坑降水的三维非稳定渗流场的计算建模和降水疏干过程进行了数值模拟研究。利用5口井和8口井的群井抽水试验资料,对模型主要参数进行了校正及后继检验计算。在上述基础上对中心基坑水位降至-22m时井的布置方案进行了优化设计,同时分析了深基坑内外渗流场的变化,为深基坑降水设计和施工提供了依据。     

TLM法在二维非均匀介质电磁场计算中的应用

传输线模型方法(Transm ission Line Modeling,TLM)是近年来发展起来的描述快速电磁场现象的分支。我们将TLM方法应用于二维介质电磁场的计算,并且详细地阐述了该算法的实现过程。在数值实验中,分别使用TLM法、有限差分法计算各向同性介质中的静电场的分布,通过对结果进行对比分析,证明了TLM方法具有较高的精度,并且用TLM方法计算电磁场相当直观。同时,还用TLM法计算了在二维非均匀各向同性介质中,点电流源情况下研究区域中的电位分布,其结果较为理想。     

湖北省城市经济地域分异规律研究

作为经济发展的重要载体,城市经济在整个区域经济格局中占据愈来愈重要的地位。以湖北省37个城市为研究对象,从定量的角度对各城市经济实力进行评价,在此基础上分析和探讨其分布特征与地域分异规律。地域分异特征有:城市分布密度差异显著,东部相对密集,西部则相对稀疏;综合实力较强的城市分布较为均衡。地域分异规律主要表现为:自然地域分异决定城市的社会经济分异的基本格局;主要城市特别是较发达城市呈现出沿主要江河沿岸和交通沿线扩展的点轴式的地域分异规律;能矿资源的地域组合及开发决定了能矿工业基地和一些矿业城镇的地域分异;区位、资源、劳动力、技术、市场、政策等要素的地域组合决定城市的经济地域类型与综合实力。并以此为基础提出各城市经济发展的相应对策。     

Lagrangian Stochastic Models For Turbulent Dispersion In The Atmospheric Boundary Layer

A one-particle three-dimensional stochastic Lagrangian model fortransport of particles in a horizontally-homogeneous atmosphericsurface layer with arbitrary one-point probability density functionof Eulerian velocity fluctuations is suggested. A uniquely definedLagrangian stochastic model in the class of well-mixed models isconstructed from physically plausible assumptions. These assumptionsare: (i) in the neutrally stratified horizontally homogeneous surface layer, the vertical motion is mainly controlled by eddies whose size is of order of the current height; and (ii), the streamwise drift term is independent of the crosswind velocity. Numerical simulations for neutral stratification have shown a good agreement of our model with the well-known Thomson's model, with Flesch and Wilson's model, and with experimental measurements as well. However there is a discrepancy of these results with the results obtained by Reynolds' model.     

基于遥感和GIS的中国植被指数变化的驱动因子分析及模型研究

在样带和典型区研究的基础上,采用相关分析和偏相关分析方法,对影响植被指数变化的因子（水、热和地表植被覆盖类型）进行了分析。结果表明：中国植被指数的时空变化极其复杂,虽受水、热和地表植被覆盖类型三个主导因子的影响和控制,但因时和因地而异,三者对植被指数影响和控制的主导地位也因时因地而不同;基于空间上的概念模型Indv=F(x,y,z)只能定性地描述以上三个主导因子时空变化同植被指数的相互关系。