Reflection and transmission ofSH waves in an initially stressed medium consisting of a sandy layer lying over a fluid-saturated porous solid

Biot's theory is employed to study the reflection and transmission ofSH waves in a sandy layer lying over a fluid-saturated porous solid half-space. The entire medium is considered under constant initial stress. Effects of sandiness, initial stress, anelasticity and viscosity of the interstitial fluid on the partitioning of energy are studied. In the presence of initial stress the incident wave starts attenuating when incider beyond a certain angle (depending upon the amount of initial stress), even if the medium is perfectly clastic. Anelasticity of the solid layer results in the dissipation of energy during transmission. The direction of attenuation vector of incident wave affects the dissipation energy to a large extent. Effect on partitioning of energy reverse at incidence after the critical angle. A complete account of energy returmed back to the underlying half-space and that which is dissipated in the overlying layer has been discussed analytically as well as numerically.     

Denudation rates of crystalline rock in the Huangling anticline of the Three Gorges of the Yangtze River in China since the Eocene

The processes and rates of the weathering denudation of the bare crystalline rock are important problems in the field of geosciences[1—6]. Essentially, the weathering denudation process is the process of rock destruction and transportation. In different …     

Geochemical engineering; taking stock

Geochemical engineering makes use of optimized geochemical processes for the solution of environmental problems. It has developed in a few years from a collection of unrelated scientific and technological incidents into a coherent concept about how and where we can improve our geo-environment. All solutions to problems of pollution are based on neutralization/breakdown, concentration, dilution, isolation or immobilization, which serve to eliminate the pollutant, make it more manageable, or prevent its entry into the mobile phase, usually water, from which it can affect the biosphere. All of these solutions have their counterpart in nature, where many examples are found of high concentrations of potentially harmful substances. A major prerequisite of geochemical engineering solutions is that they should be compatible with the natural evolution of the system in its geo-environment. The advantages of this approach are that we can devise low-cost technologies (nature does most of the hard work itself), interfere least with nature, and quite often end up with useful by-products. Disadvantages are that technologies based on natural geochemical processes tend to be slow. The application of geochemical engineering concepts requires a better understanding of our environment and its ongoing processes than is necessary for a ‘classical' technology. In most environmental technologies the conditions are externally imposed on the system to be treated, and the natural evolution of the system is eliminated, or at best neglected. The concept of seeking a closer conformity with nature is paralleled in other disciplines like agriculture or the medical sector, where we see a similar evolution in the direction of techniques that are more in harmony with nature. Geochemical engineering brings many advantages, particularly in developing countries, or in countries where the state of the economy does not permit the introduction of expensive high-tech environmental technologies. So far, most of the applications of geochemical engineering concepts have focussed on solutions to environmental problems, but there are a number of cases where the environmental issue is more indirect, as e.g. in civil engineering. Geochemical engineering may be practised on a large, almost global scale, down to that of individual minerals, in accordance with the fact that geochemical processes also act on vastly different scales. An overview will be given of some of the problems that are being studied.     

南海热带气旋路径集合预报试验

利用3种不同模式的初始资料,通过它们生成得到16个不同的初始场,分别对2004年南海及其周边地区9个热带气旋个例进行集合预报试验,最后筛选得到了7个南海热带气旋初值集合成员,由此初步探讨了南海热带气旋初值集合成员的生成方法。结果表明,采用不同模式的初始资料生成得到初值集合成员的方法用于集合预报,对南海热带气旋路径预报有一些明显的改进。     

顾及起算数据误差的整体平差法

因起算数据误差的存在 ,导致了用普通的平差方法求得的结果精度降低。本文提出了顾及起算数据误差的计算方法 ,即从整体平差的角度出发 ,将起算数据作为虚拟观测值 ,与观测值一起进行平差。     

蒲石河抽水蓄能电站地下厂房三维初始应力场反演分析

采用三维非线性有限元反演回归分析计算方法,提出侧压力系数函数拟合方法,考虑了地质构造,地形地貌以及实测应力对初始应力场的影响。对蒲石河抽水蓄能电站地下厂房区域初始地应力场进行反演回归分析研究,实测点处附近应力分布的局部特性证明反演计算方法是合理的。     

关于Mckenzie沉积盆地初始沉降公式的修正

根据Airy均衡原理对Mckenzie沉积盆地初始沉降公式进行了修正,并导出了公式的正确表达式 S=(a[(ρ_o-ρ_c)t_c/a(1-(aT_1t_c)/(2a))-(aT_1ρ_o)/2](1-1/β))/(ρ_o(1-aT_1)-ρ_w)     

采用因子分析法计算下庄铀矿田航放初始铀含量

采用因子分析对下庄铀矿田的航测K、U、Th数据进行了主成分分析,指出第一主成分反映母体的原始放射性元素含量及其分布状况,并利用U在PC1上的因子负荷反映铀的原始沉积。     

基于假反扰动的江淮梅雨锋低涡初始误差分析

以一个江淮梅雨锋低涡的48h模拟结果为基态计算了奇异矢量,并利用奇异矢量构造了假反扰动。分析表明,假反扰动能在一定程度上描述初始误差,可以借助其进行初始误差分析;在假反扰动中,发展缓慢的奇异矢量分量是主体,描述了绝大部分模拟误差且增长迅速的奇异矢量所占比例却很小;分析假反扰动的具体形势发现850hPa上初始误差主要是低涡西南方向的低压槽偏弱,而在500hPa,渤海湾低压槽向西南方向的伸展不够,低压槽东边的高压脊应进一步向北伸展,这些初始误差都分布在关键系统的周围,并且具有中尺度的特征。另外,假反扰动中不同物理量场改进预报质量的贡献各不相同,各种物理量场间存在着使其空间分布趋于一致的动力相关关系。