Contamination of a well in a uniform background flow

In this paper we describe the transport of pollution in groundwater in the neighbourhood of a well in a uniform background flow. We compute the rate at which contaminated particles reach the well as a function of the place of the source of pollution. The motion of a particle in a dispersive flow is seen as a random walk process. The Fokker-Planck equation for the random motion of a particle is transformed using the complex potential for the advective flow field. The resulting equation is solved asymptotically after a stretching transformation. Finally, the analytical solution is compared with results from Monte Carlo simulations with the random walk model. The method can be extended to arbitrary flow fields. Then by a numerical coordinate transformation the analytical results can still be employed.     

Textural analysis and modelling of a flood deposit: River severn,U.K.

Samples of sediment collected from the Severn floodplain between Worcester and Gloucester following the severe flooding in January and February 1990, were analysed for their grain size distribution. The results show that most sand was deposited within 20 m of the channel bank, but that fine sand may contribute to flood sediment across the width of the floodplain. James' (1985) numerical model of overbank sedimentation attempts to predict the transfer of sediment to the floodplain during flooding. Geometrical and hydraulic data relating to the Severn flood are used as input for a computer program of James' (1985) model. The pattern of sediment concentrations predicted by the model was compared with that obtained from statistical analysis of the flood sediment. The patterns were found to be similar, so James' (1985) model was considered to predict in a relative sense the distribution of flood sediment.     

建立涌水量曲线方程的最小残差法

本文在综述了目前稳定流涌水量经验方程建立方法的基础上,根据最小二乘法原理,提出了一种新的方法—最小残差法,并给出了计算实例。计算表明,最小残差法是建立稳定法涌水量经验方程的一种较好方法,计算过程在微机上易于实现。     

Numerical algorithm for the dynamic analysis of base-isolated structures with dry friction

This paper deals with the techniques for solving ordinary differential equations with essential nonlinearity arising from the representation of frictional force by the sign function of the relative velocity. This problem is connected with dynamic behavior studies of base-isolated structures with dry friction devices.Mathematical evidence is presented concerning the inaccuracies of the solution which are connected with the representation of the frictional force by the sign function. An approximation of this sign model is made on the basis of the appropriate linearization of a small part of the frictional force function. A numerical algorithm for the dynamic analysis of base-isolated structures with dry friction is proposed. Numerical tests are carried out for establishing the exactness of the proposed techniques. The obtained results prove the accuracy of the techniques.     

黄海粘土沉积物的来源与分布

本文根据区域自然地理原理,划分黄海粘土沉积物的补给区,在粘土矿物鉴定的基础上,用法方程定量探明黄海粘土沉积物的来源与分布,绘出黄海粘土沉积物分布图。图示:黄海来源于长江的粘土沉积物的分布面积,占其总面积的56.5%,来源于黄河的占43.5%。粘土沉积物的分布同洋流、海流的分布相吻合。     

自聚焦光纤中传导模的场分布

从亥姆霍兹方程出发，导出了自聚焦光纤中传导模在圆柱坐标系中的场分布形式，并给出了几个低阶模的分布图。     

Experimental diffusion of hydrogen into synthetic fluid inclusions in quartz

Abstract Quartz-hosted, synthetic CO₂-H₂O fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory-simulated metamorphic re-equilibration at 650, 750 and 825°C and 1.5 kbar total pressure with f_O2 defined by the C-CH₄ buffer. Microthermometry and Raman spectroscopy show that the initial CO₂-H₂O inclusions become CO₂-CH₄-H₂-H_2O
inclusions after diffusive influx of hydrogen from the reducing confining medium. Measurable changes are observed in inclusion compositions after only 15 days of re-equilibration, implying significant hydrogen mobility at still lower temperatures over geological time spans. Results of synthetic inclusion re-equilibrium experiments have profound implications for the interpretation of natural fluid-inclusion data; failure to account for potential hydrogen migration in inclusions from high-temperature geological environments may lead to erroneous estimates of P-T, and/or the compositions of metamorphic fluids.     

偏微分方程数值解法在地学应用中的对比分析

在地学中广泛应用的偏微分方程数值解法有两种:有限差分法及有限单元法。对于定常态问题两种方法完全等价,对于非定常态问题有限单元法形成的代数方程归根到底仍是有限差分方程,但在一定条件下会引起反常问题,原因是与代数组相容的不是原来的热传导方程,而是反热传导方程。