基于MCI指数的福建省干旱气候特征

采用目前国家干旱监测业务实行的MCI指数,利用Morlet小波、经验正交函数（EOF）等方法,分析了福建省1961—2019年全省66个气象站MCI指数表征的干湿状况和干旱变化特征。结果表明：福建省存在明显的干湿气候特征,具有显著的6—8 a和22 a的周期振荡,内陆山区干湿变化周期比沿海长,在季节尺度上各季均存在多时间尺度和地域差异化的特点;其空间变化具有3种典型模态,反映了季风降水多寡和地形差异。MCI表征的干旱过程时空分布与历史干旱事件相吻合,秋季和冬季是福建省干旱发生频率最高的季节,春季和夏季是干旱强度最强的季节;闽江口以南沿海地区干旱发生率明显高于内陆地区,全省出现同步干旱的机率较小（12%）。     

论城市地下管线MIS与城市规划管理的关系——以胶南市城市地下管线MIS为例

在分析山东省胶南市城市地下管线M IS的基础上,从两个方面论述了城市地下管线与城市规划管理的关系,认为城市地下管线M IS和城市规划管理之间相互作用、互为补充、关系密切。城市地下管线M IS为城市规划管理工作提供了准确而有现势性的基础资料,提高了规划管理的工作效能和城市规划管理水平;城市规划管理保障了城市地下管线M IS数据的动态更新和现势性,实现地下管线从规划设计审批竣工测量,到系统数据更新的全过程动态管理。     

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.     

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.     

PARAMETER AND VARIANCE ESTIMATION IN GEOTECHNICAL BACKANALYSIS USING PRIOR INFORMATION

A probabilistic framework to perform inverse analysis of geotechnical problems is presented. The formulation allows the incorporation of existing prior information on the parameters in a consistent way. The method is based on the maximum likelihood approach that allows a straightforward introduction of the error structure of field measurements and prior information. The difficulty of ascribing definite values to the uncertainties associated with the various types of observations is overcome by including the corresponding variances in the set of parameters to be identified. The inverse analysis results in a minimization problem that is solved by coupling the optimization technique to the finite element method. Two examples are presented to illustrate the performance of the method. The first one corresponds to a synthetic case simulating the excavation of a tunnel. Young's modulus, K₀ value and measurements variances are identified. The second case concerns the excavation of a large underground cavern in which again Young's modulus and K₀ are identified. It is shown that introduction of prior information permits the estimation of parameters more consistent with all available informations that include not only monitored displacements but also results from in situ tests carried out during the site investigation stage.     

FINITE ELEMENT MODELLING FOR LAND DISPLACEMENTS DUE TO PUMPING

Equations of equilibrium (force balance) and flow in multidimensions were coupled in this paper to describe land displacements due to pressure decline in aquifers. A Galerkin finite element model based on these equations was developed. The saturated/unsaturated behaviour and the isotropic/anisotropic properties of permeability and elasticity were considered when the model was formulated. This model was verified by comparing its simulation results with those of known analytical solutions for simplified cases. The simulation of displacements due to pressure decline in unsaturated media was also performed. Those results demonstrated that the choice of boundary ranges for an aquifer with infinite domain may significantly affect the estimated horizontal and vertical displacements. To obtain a good estimation of land displacements, the boundary ranges should be carefully chosen. The displacements occurring in unconfined aquifers are caused by the drop of the water table and the change in body force in the dewatering zone. Simulation results also indicated that the change in body force should be considered once an unconfined aquifer has been pumped. Otherwise, the horizontal and vertical displacements in unconfined aquifers would be overestimated and underestimated, respectively. The behaviour of land displacements due to pumping was shown to be affected by changes in the total stresses in aquifers.     

THE ‘NEW IMPLICIT METHOD’ FOR TUNNEL ANALYSIS

Tunnel excavation is a coupled three-dimensional problem dealing with two different structures: lining and rockmass. For a simple application it is useful to develop simplified methods by treating the problem as plane strain. If the problem of tunnel face advance presents an axisymmetric geometry, then we show that the major parameter governing the ground–interface–lining interaction is the convergence of the tunnel U₀ at the moment of the lining installation. The ‘New Implicit Method’ (NIM) presented in this paper makes use of principles similar to those of the ‘convergence–confinement’ method, but it provides a better appreciation of the coupled behaviour of rockmass and lining. For independent time constitutive laws (elasticity and plasticity), we point out that the convergence U₀ depends not only on the mechanical behaviour of the rockmass and on the distance from the tunnel face, as predicted by the ‘convergence–confinement’ method, but also on the stiffness of the lining previously set. We present the ‘NIM’ for elastic and perfect elastoplastic rockmasses without dilatancy for many criteria. The development of this new method is based on the results of tunnel calculations with an axisymmetric FEM numerical model that takes into account the three-dimensional aspect of the problem. Using this method is simple and its results agree well with the FEM numerical results. Its accuracy is highly satisfactory for a geotechnical study.     

三维CT成像的数学模型

三维CT成像广泛应用于放疗模拟定位等临床实践。当扫描运动物体时三维图像存在的位移和形变,与扫描参数设置和被扫描物体的运动状态等关系密切。本文通过理论分析CT扫描过程,建立三维成像的数学模型,计算三维图像的时间分辨率、位移和形变等指标,并分析其变化规律,为将来进一步的实验研究奠定基础。     

应用核磁共振成像(NMRI)技术研究复合剂驱油特征

本文应用核磁共振成像技术,在均值、非均值模型中研究了复合剂驱油动态实验过程。观察及分析了复合剂驱油特征和效果,对复合剂驱油段塞前缘进行了实时跟踪,得到了复合剂驱油段塞前缘油墙的形成及剩余油分布与运移的二维图像,给出了复合剂驱油后,剩余油的饱和度分布曲线。实验表明:在层状非均值地层中,若渗透率差异大,复合剂段塞主要进入高渗层,而波及不到低渗层,即复合剂波及效率低。若渗透率差异小,复合剂段塞大部分进入高渗层,有少部分进入低渗层,即复合剂波及效率较高。