层状饱和地基上刚性圆板的扭转振动及参数分析

用解析的方法首次研究了层状饱和地基上刚性圆板的扭转振动特性.运用Hankel变换求解饱和介质动力问题的控制方程,按混合边值条件建立了层状饱和地基上刚性圆板扭转振动的第二类Fredholm积分方程.数值算例给出了动力柔度系数和扭转角幅值随无量纲频率的变化曲线,与单相弹性及匀质饱和介质情况进行了对比分析,并进行了参数研究.     

Cavernous weathering,dynamical instability and self‐organization

Cavernous weathering may be conceptualized as a self‐reinforcing process, characterized by positive feedback within the weathering system. A morphometric study of caverns in the Valley of Fire State Park, Nevada, USA, demonstrates the applicability of a dynamically unstable, or conditionally unstable, model of cavernous weathering systems. Outcrop surfaces displaying caverns tend to show increasing fragmentation of the surface in the early stages of cavernous weathering, succeeded by convergent evolution of the surface in which caverns tend to grow and coalesce. A paradoxical relationship exists between the weathering system output at the scale of individual forms and the outcrop scale: caverns tend toward minimum interior surface area by developing a spheroidal form, yet the outcrop surface tends toward maximum exposed surface area by increasing the degree of fragmentation of the surface. Copyright © 2004 John Wiley & Sons, Ltd.     

Divergent evolution in fluviokarst landscapes of central Kentucky

Central Kentucky is characterized by a mixture of karst and ?uvial features, typically manifested as mosaic of karst‐rich/channel‐poor (KRCP) and channel‐rich/karst‐poor (CRKP) environments. At the regional scale the location and distribution of KRCP and CRKP areas are not always systematically related to structural, lithological, topographic, or other controls. This study examines the relationship of KRCP and CRKP zones along the Kentucky River gorge area, where rapid incision in the last 1·5 million years has lowered local base levels and modi?ed slopes on the edge of the inner bluegrass plateau. At the scale of detailed ?eld mapping on foot within a 4 km² area, the development of karst and ?uvial features is controlled by highly localized structural and topographic constraints, and can be related to slope changes associated with retreat of the Kentucky River gorge escarpment. A conceptual model of karst/?uvial transitions is presented, which suggests that minor, localized variations are suf?cient to trigger a karst–?uvial or ?uvial–karst switch when critical slope thresholds are crossed. Copyright © 2004 John Wiley & Sons, Ltd.     

基于集对分析的水资源变化趋势的统计预测

根据集对分析(SPA)的原理和方法，对水资源变化趋势的预测进行了研究。利用前期的预测因子进行计算，可以使集对分析具有预测功能。通过反复调整预测因子各区段的分界值，可以使水资源要素计算等级和实际等级的历史拟合率达到最大，其结果是比较好的。这是对水资源变化趋势的预测研究的一种新尝试。     

基于模糊控制的土地价格评估

随着我国土地使用制度改革的不断深化，土地价格已成为调节土地供给和需求，促进土地使用权合理流动、合理配置和产生最大效益的重要手段．科学评估土地价格成为我国土地使用制度深化改革的客观需要。文章以模糊数学理论为基础，针对土地估价方法中市场比较法的不足，提出了应用模糊(Fuzzy)控制理论进行地价评估，井建立了土地价格评估的模糊控制预测模型，运用实例对模型的可靠性进行了验证，证明模糊控制理论应用于土地价格评估是可行的，具有一定的实用价值，实现了土地价格评估的科学化、自动化。     

基于时间序列分析的动态变形预测模型研究

提出了基于AR并将其推广到CAR模型对时间序列统一建模的新观点和方法，并以实例对动态模型与静态模型分别作了应用比较。结果表明，时间序列分析动态模型预测精度高，用途广泛。     

遗传算子对径流预报神经网络模型的影响

采用均匀设计来安排遗传算子组合进行数值实验,研究了遗传算子对神经网络径流预报精度的影响。研究发现,输入模式对最终种群中个体的分布影响不明显,不同算子组合对其影响则明显得多。通过回归分析发现,采用不同算子组合优化神经网络初始权重径流预报精度差别较大,对未归一网络的优化效果较归一网络好,同时采用数据归一输入模式与遗传算法优化神经网络初始权重未产生叠加效果。     

山东主汛期暴雨分析及预报研究综述

对山东天气预报工作者的暴雨分析和预报研究成果进行了总结和评述，从天气预报业务角度提出今后需要着重研究的领域。     

松散地层钻孔涌水量预报方法研究

本文在讨论岩土饱和度与视电阻率关系的基础上,采用数理统计方法对天水盆地20口井的钻孔涌水量和视电阻率数据进行分析,建立了该地区松散层钻孔涌水量预报回归模型.选用一眼供水井实测数据对预报回归模型进行检验,实际涌水量与模拟值比较,两者相对误差为8.9%;进而采用该回归模型对其它供水井涌水量进行了预报,实际涌水量与预报值相比较,相对误差分别为7.0%、29.5%.结果表明,在河谷潜水井施工中,所建立的涌水量预报回归模型可在成井、抽水前预先估算钻孔涌水量,为地质与钻探决策提供了一定科学依据.     

On the Behavior of the Stable Boundary Layer and the Role of Initial Conditions

Previous studies of the stable atmospheric boundary layer using techniques of nonlinear dynamical systems (MCNIDER et al., 1995) have shown that the equations support multiple solutions in certain parameter spaces. When geostrophic speed is used as a bifurcation parameter, two stable equilibria are found—a warm solution corresponding to the high-wind regime where the surface layer of the atmosphere stays coupled to the outer layer, and a cold solution corresponding to the low-wind, decoupled case. Between the stable equilibria is an unstable region where multiple solutions exist. The bifurcation diagram is a classic S shape with the foldback region showing the multiple solutions. These studies were carried out using a simple two-layer model of the atmosphere with a fairly complete surface energy budget. This allowed the dynamical analysis to be carried out on a coupled set of four ordinary differential equations. The present paper extends this work by examining additional bifurcation parameters and, more importantly, analyzing a set of partial differential equations with full vertical dependence. Simple mathematical representations of classical problems in dynamical analysis often exhibit interesting behavior, such as multiple solutions, that is not retained in the behavior of more complete representations. In the present case the S-shaped bifurcation diagram remains with only slight variations from the two-layer model. For the parameter space in the foldback region, the evolution of the boundary layer may be dramatically affected by the initial conditions at sunset. An eigenvalue analysis carried out to determine whether the system might support pure limit-cycle behavior showed that purely complex eigenvalues are not found. Thus, any cyclic behavior is likely to be transient.