抚河中游地区几个地貌第四纪地质问题   总被引：1，自引：0，他引：1  

张金城 《华东地质学院学报》1989,12(3):43-46

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A survey of numerical methods for stochastic differential equations     

P. E. Kloeden  E. Platen 《Stochastic Hydrology and Hydraulics》1989,3(3):155-178

The development of numerical methods for stochastic differential equations has intensified over the past decade. The earliest methods were usually heuristic adaptations of deterministic methods, but were found to have limited accuracy regardless of the order of the original scheme. A stochastic counterpart of the Taylor formula now provides a framework for the systematic investigation of numerical methods for stochastic differential equations. It suggests numerical schemes, which involve multiple stochastic integrals, of higher order of convergence. We shall survey the literature on these and on the earlier schemes in this paper. Our discussion will focus on diffusion processes, but we shall also indicate the extensions needed to handle processes with jump components. In particular, we shall classify the schemes according to strong or weak convergence criteria, depending on whether the approximation of the sample paths or of the probability distribution is of main interest.  相似文献   

热流测量中垂向地下水运动干扰的校正方法   总被引：2，自引：0，他引：2       下载免费PDF全文

胡圣标  熊亮萍 《地质科学》1994,29(1):85-92

本文提出了一种地表热流测量中垂向地下水干扰的校正方法。并以江西萍乡和福建安溪的二个钻孔为例,说明了热流校正的具体过程。由于地下水对流传热的影响,垂向地下水渗透层内温度和热流随深度均呈指数分布。通过对钻孔测温数据的一维垂向Peclet数分析,可以确定渗透层内传导和对流热流分量以及热流的构成,从而得到未受地下水对流干扰的区域背景热流。这一方法不仅适用于渗透率结构均一的介质,也可用于水平层状介质。  相似文献   

滇中郝家河砂岩铜矿的地球化学及其成因意义   总被引：1，自引：0，他引：1  

秦德先  马宏 《地质论评》1994,40(2):183-192

本文论术字滇中生代地层与矿区及春外围马头山组中铜的时空分布与迁移富集规律，揭示了矿床的沉积－后期叠加改造成因。成矿作用经历了同生沉积形成矿源层，后期叠加改造形成矿体的过程。后期改造中铜元素发生了大量迁移，矿质主要来自矿体之下伏紫色矿源层。  相似文献   

淮南市区浅层地下水求参公式的建立     

许多顶  钱谋始 《安徽地质》1994,(4)

根据淮南市区浅层地下水埋深浅，滞后效应小等特点，推导出一套实用的水文参数计算公式，包括：降水入渗补给地下水系数ａ，蒸发极限深度Ｌ，蒸发系数Ｃ，以及浅层地下水的给水度ｕ的计算公式。  相似文献   

Dynamics of fluvial and slope processes in the changing geomorphic environment of singapore     

Kalyani Chatterjea 《地球表面变化过程与地形》1994,19(7):585-607

The nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in Singapore. Storm-based and time-based data, from undisturbed rainforests, heavily disturbed construction sites, urban grass-covered slopes and an experimental plot, are collected to observe the impact of rainwater on the soil moisture conditions, surface microtopography, runoff generation, sediment movement, and ground lowering in the three different categories of land use. The undisturbed forested environment is characterized by high throughfall (58% of total rainfall) and frequent negative soil moisture suctions. The slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography. No rills develop. Ground lowering is recorded as 3·2–3·4 mm a^?1. But sediment movement is episodic and suspended sediment concentrations in overland flow are 172–222 mg l^?1. During urban construction, gully development is rapid on the bare slopes, runoff generation, voluminous, and sediment-laden discharges (5200–75498 mg l^?1) lead to sediment plumes at channel mouths. Ground lowering rates are measured at 132·4 mm a^?1. Once grass-covered, runoff carries less suspended sediment (800 mg l^?1) and ground lowering rates are reduced, but depend on the condition of the cover, ranging from 0·2 to 8·2 mm a^?1. As urban development continues, environments are altered both in time as well as spatially.  相似文献   

水网区区域水位模型及其应用   总被引：1，自引：0，他引：1       下载免费PDF全文

宋克强  王兴祥 《水科学进展》1995,6(3):205-210

水网区在宏观尺度上可被视为一种连续介质,可用水在多孔介质中的运动来比拟水网中水的运动.在这种概化条件下,推求出水网区水体运动的表述方法.利用这一方法建立的太湖水网区区域水位模型,与实际情况相比,获得了较好的效果.  相似文献   

关于部分变元的非常稳定性     

湛少锋 《武汉大学学报(信息科学版)》1990,(4)

本文利用极限方程的方法研究微分方程关于部分变元的多种非常稳定性,讨论了给定方程与其积限方程的非常稳定性的关系。  相似文献   

铀矿层真实厚度的确定和最佳测井点距          下载免费PDF全文

秦积庚  谭庆江 《地球物理学报》1990,33(4):468-479

本文讨论了最佳测井点距的选择原理,其最佳值大致为8-12.5cm.并从原理上分析了矿层解释厚度增大的主要原因:根据离散测量值所作的分层解释结果必然导致矿层解释厚度的增大.大量的模型测量结果完全证实了理论分析的正确性,并且还提出了合适的解决办法.  相似文献   

太白山古冰川地貌与地质构造     

夏正楷 《冰川冻土》1990,(4)

太白山分布有更新世冰川地形,其冰川槽谷在平面上呈“十”字型排列;横剖面EW向的呈宽谷形,NS向是呈U型:纵剖面EW向比较平坦,SN向呈阶梯状,其中有许多断裂陡坎。冰斗均位于断裂交汇点,面积不大而深度却相当大。这些地形的形态特征可以用构造加以解释,断裂破碎带是最有利于冰川刨蚀的地段。  相似文献