Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

The radiance leaving the earth-atmosphere system which can be sensed by a satellite borne radiometer is the sum of radiation emission from the earth surface and each atmospheric level that are transmitted to the top of the atmosphere. The radiation emission from the earth surface and the radiance of each atmospheric level can be separated from the radiance at the top the atmospheric level measured by a satellite borne radiometer. However, it is very difficult to measure the atmospheric radiance, especially the synchronous measurement with the satellite. Thus some atmospheric radiative transfer models have been developed to provide many options for modeling atmospheric radiation transport, such as LOWTRAN, MODTRAN, 6S, FASCODE, LBLRTM, SHARC, and SAMM. Meanwhile, these models can support the detailed detector system design, the optimization and evaluation of satellite mission parameters, and the data processing procedures. As an example, the newly atmospheric radiative transfer models, MODTRAN will be compared with other models after the atmospheric radiative transfer is described. And the atmospheric radiative transfer simulation procedures and their applications to atmospheric transmittance, retrieval of atmospheric elements, and surface parameters, will also be presented.     

EFFECT OF SLAB FLEXIBILITY ON INTERACTION BETWEEN TWO CIRCULAR FOUNDATIONS

The paper is aimed at investigating the effect of foundation rigidity on dynamic stiffness for two circular foundations on a viscoelastic medium. To generate the dynamic stiffness, a substructure technique is employed. For the substructure of a viscoelastic medium, the solution for wave motion reported in Reference 11 is used. For the substructures of two flexible foundations, classical plate theory with the inertial force neglected is employed to find the displacement fields of the foundation plates subjected to the interaction stresses. Then, the continuity condition for all the substructures is imposed implicitly by using the variational principle; then with the help of the reciprocal theorem the dynamic stiffness for the two flexible foundations can be obtained. For the numerical study, the boundary condition at the rims of both foundation plates is assumed to be a hinge connection to superstructures. Some numerical investigations are performed and the effect of foundation rigidity on dynamic stiffness is examined. Some discussions and conclusions are also made.     

THE THEORY OF RESPONSE ANALYSIS OF FUZZY STOCHASTIC DYNAMICAL SYSTEMS WITH A SINGLE DEGREE OF FREEDOM

Most real-life structural/mechanical systems have complex geometrical and material properties and operate under complex fuzzy environmental conditions. These systems are certainly subjected to fuzzy random excitations induced by the environment. For an analytical treatment of such a system subjected to fuzzy random excitations, it becomes necessary to establish the general theory of dynamic response of a system to fuzzy random excitations. In this paper, the theory of response, fuzzy mean response and fuzzy covariance response of a single-degree-of-freedom (sdf) system to fuzzy random excitations in the time domain and frequency domain is put forward. The theory of response analysis of an sdf system to both stationary and non-stationary fuzzy random excitations in the time domain and frequency domain is established. Two examples are considered in order to demonstrate the rationality and validity of the theory, and the models of stationary filtered white noise and non-stationary filtered white noise fuzzy stochastic processes of the earthquake ground motion are set up. Methods of analysis for fuzzy random seismic response of sdf systems are put forward using the principles of response analysis of an sdf fuzzy random dynamic system.     

DYNAMIC CROSS-INTERACTION BETWEEN FLEXIBLE SURFACE FOOTINGS BY COMBINED BEM AND FEM

A combined boundary and finite element method is developed and applied to study the dynamic behaviour of a system of flexible surface footings of arbitrary shape bearing on an elastic half-space. The proposed method employs the frequency domain Green's function for the surface of the elastic half-space while a layered plate model is used for the flexible footing. Both the footing and the surface of the half-space are discretized by 8-noded quadratical isoparametric elements, and the meshes are identical. Thus, the compatibility of displacements and equilibrium of forces between the footing and the half-space are fully satisfied. This model provides a better approximation of the stress concentration at edges of relatively rigid footings. Numerical examples demonstrating the effects due to the excitation frequency, the relative rigidity and the distance between footings on the interaction between two square footings are presented. The external forces can be either harmonic or transient.     

ON THE CHARACTERISTICS OF NON-LINEAR SOIL RESPONSE AND DYNAMIC SOIL PROPERTIES USING VERTICAL ARRAY DATA IN JAPAN

Non-linear response of the soil is investigated by comparing the spectral ratios (uphole/downhole) using weak and strong motions. Data from seven vertical arrays in Japan are analysed in this study. The frequency-dependent transfer function of soil is calculated as a ratio of the spectrum at uphole to the spectrum at downhole, considering the horizontal component of shear wave. In spectral ratio analysis auto- and cross-spectra are employed. The reduction in the predominant frequency of the transfer function with increases in excitation level reflects the non-linear response of the soil. Results of analysis demonstrate a significant non-linear ground response at six sites with surface PGA exceeding 90 gal. However, the results of one site show the linear response up to 130 gal surface PGA. Furthermore, the in situ strain-dependent soil behaviour is examined through the shear modulus – shear strain relationship. When compared, the actual and laboratory results of the shear strain – shear modulus relationship are in agreement. Additionally, a good consistency between the tendency of reduction in shear modulus ratio with shear strain increases, and reduction of predominant frequency with ground motion increases, confirms the significance of non-linearity in site effects study.     

超声回弹综合法检测单一构件混凝土强度推定值的保证率分析

在实际工程检测数据的基础上,利用M on te C arlo试验对单一构件混凝土强度推定值的保证率问题进行了分析。30片梁板实测数据分析结果表明:将构件各测区混凝土强度换算值的最小值作为该构件的混凝土强度推定值的保证率范围为79.0%~94.2%,小于《超声回弹综合法检测混凝土强度技术规程》(CECS 02:88)规定的95%保证率要求,因此,对结构性能鉴定而言该混凝土强度推定值是偏于不安全的,应引起试验检测人员的充分重视。     

区域生态安全动态变化及空间差异定量分析:以陕北黄土高原为例

1 Introduction Ecological security is defined as the goal of stakeholders to create a condition where the physical surroundings of a community provide for the needs of its inhabitants without diminishing its natural stock (Chen, 2002; Wachernagel et al.,…     

基于动态分段技术的城市公交系统数据库的建立

针对应用传统GIS弧段-结点拓扑数据模型在建立线性要素的空间数据库中面临的问题,文中采用了应用动态分段技术构建城市公交系统数据库的技术方案,然后详细介绍了在动态分段思想指导下系统数据库的建立过程,并建立了芜湖市公交查询系统的数据库。实验表明应用动态分段技术来组织系统数据能够很好地实现在不增加系统数据物理存储容量的基础上可以很好地实现系统信息的按需分配。     

烃源岩地质色层效应的模拟实验

利用未混油或混油源岩样品在低温、加压条件下分别对纹层状泥岩、暗色块状泥岩及灰质块状泥岩样品进行排烃模拟实验,其中块状泥岩及灰质块状泥岩被研碎后混入同层原油,而纹层状泥岩不被研碎(也未混油),以保持其层理结构的完整性。实验结果显示,排烃过程造成轻烃相对富集,色谱图中主峰碳前移,正构烷烃分布及部分甾、萜烷参数值在排烃过程中产生明显变化,萜烷对运移的敏感性没有甾烷强。在排烃过程中纹层状泥岩与块状泥岩及灰质块状泥岩的地质色层效应有着显著的差异,相对而言,块状泥岩与块状灰质泥岩的排烃效率低,但排烃过程造成了它们出现较为明显的地质色层效应,而纹层状泥岩排烃效率高,但在排烃过程中地质色层效应不明显。分析认为源岩的物理结构是造成这种地质色层效应的差异的主要原因之一。     

东营凹陷砂岩透镜体油气成藏机理及有利区预测

近几年济阳坳陷的勘探实践表明, 对岩性油藏的含油性差异、成藏机理尚认识不清, 这制约了隐蔽油气藏的进一步勘探.在东营凹陷145个砂岩透镜体油藏含油性统计分析的基础上, 结合典型透镜体油藏详细解剖和核磁共振物理模拟实验结果综合研究后发现: 砂岩透镜体圈闭形成时的构造和沉积环境、围岩生排烃条件、砂体储集条件是其成藏的主控因素.只有围岩(源岩) 进入供烃门限后, 其与砂体界面处的毛管压力差、烃浓度梯度产生的扩散力和膨胀力3者之和大于砂体中过剩的水向外渗滤遇到的阻力, 即成藏动力大于成藏阻力时, 砂岩透镜体才能成藏.当砂体沉积环境、围岩生排烃条件、砂体自身储集条件3方面均满足一定条件时, 圈闭才具备形成砂岩透镜体油藏的条件, 并且上述3方面条件越优越, 圈闭含油性就越好.用此方法对东营凹陷下第三系沙三中亚段砂岩透镜体油藏的分布进行了预测.