非活动隐伏断层对结构地震反应的影响

采用有限元方法分别建立了包含隐伏断层和不包含断层的场地模型，分析了在各种频率水平入射波作用下该场地地面结构的动力反应。计算结果表明，隐伏断层对地面结构的动力反应有一定的放大作用，特别是当入射波的频率与场地的基频接近时，放大效应更为明显。这一结果说明，在包含隐伏断层的场地进行重大工程建设时，需要考虑断层对地震动的影响。     

BIOLOGICAL AND ECONOMIC IMPLICATIONS OF SACRAMENTO WATERSHED MANAGEMENT OPTIONS1

ABSTRACT: This paper brings together spatially and temporally explicit mechanistic models of hydrodynamic, water quality, and ecological processes with an economic model to examine water management alternatives for California's Sacramento River and Delta ecosystem, a large‐scale watershed. Overallocated water supplies in most years, combined with increasing demand for water for environmental purposes, have created a politically charged atmosphere and a need for quantitative assessment of the implications of policy alternatives. By developing and analyzing a common set of policy scenarios, this integrated framework allows us to consider tradeoffs between agricultural economic factors, water quality, and population dynamics for two at‐risk fish species. We analyze two rather extreme types of policy options; one involves structural modifications to change the flow of water within the watershed but no change in water diversions, while the other reallocates water from agricultural users to fish and wildlife. Results suggest that substantial environmental improvements could be made at a relatively modest cost to farmers (1 to 4 percent reductions in revenues) but that those costs could be significant locally. In addition to tradeoffs between farmers and environmental interests, results suggest that policy makers may need to balance competing environmental objectives.     

对DXF文件信息安全地提取机制研究

DXF文件作为AutoCAD所支持的中间文件格式 ,包含了AutoCAD工程图的全部信息。如果操作不当 ,不但得不到所需要的信息 ,而且还可能使文件的安全性遭到破坏。针对工程中提取文本图元信息这样的实际问题 ,通过研究DXF文件的构成 ,提出了实际可靠的算法 ,该算法具有一定的通用性 ,并且以word文件的格式给出得到的结果。如果需要其他图元信息 ,只要适当修改此算法就可以。     

中国地震灾害与人文要素的相关性分析

中国的地震灾害与人员伤亡为世界最严重的国家之一，这不仅由于地震多、震级大、烈度高，多数地方建筑物抗震性能较低，而且还与人文因素密切相关。本文着重讨论了人品密度与震害伤亡人数的相关性，并分析了作息时间、作业方式、地震预报、心理状态等人文要素与震害伤亡人数的相关性。     

水平地震激励下储罐液体晃动分析

在考虑地基与储罐相互作用的情况下，采用有限元法对储罐在水平地震荷载作用下的液体晃动反应进行了分析。结果表明：罐内液体的晃动是长周期运动，并且是多阶振型的组合。从与小体积罐的比较可以看出，大型储液罐的液面晃动不只是以基本振型为主，前几阶振型对液面晃动的贡献也比较显著，并且液面晃动的基本周期比小体积罐的大很多。     

火灾下大空间结构温度场的数值模拟分析

大空间结构近年来在我国得到了迅速的发展,然而,我国原有防火规范常常无法满足该类结构防火设计的需要。目前性能化设计方法是防火研究领域的发展趋势,而结构内部温度场的准确计算与否是其中非常关键的重要环节。笔者利用流体动力学计算软件FLUENT对不同火灾曲线和火源功率下,典型尺寸模型的温度场随时间与空间的分布情况进行了计算模拟,并与我国《钢结构防火技术规程》(征求意见稿)中近似公式计算结果相对比,同时对规范中未规定的火源功率可否使用已知值采用线性插值方法求解进行了讨论,并深入分析了此简化计算公式存在的局限性。     

Streambed Sediment Geochemical Controls on In-Stream Phosphorus Concentrations during Baseflow

A spatially extensive geochemical data set of stream water and bed sediment composition across the Tamar catchment in south-west England was analysed to identify the key bed sediment properties that control the in-stream dissolved reactive phosphorus (DRP) concentrations during baseflow conditions. Linear regression analysis of the streamwater DRP concentrations and the distribution coefficient K _d for DRP revealed that the former is positively correlated with total SiO₂ and Al₂O₃, and negatively correlated with K₂O. The primary control on these major element distributions is the dominant bedrock geology. The data suggest that streamwater DRP concentrations are mainly controlled by adsorption to clay minerals. Where P concentrations in streamwater were considerably elevated by inputs from point sources, DRP concentrations are also controlled by precipitation of hydroxyapatite.     

Direct and Indirect Effects of Soil Pollution by Lignite Mining

Lignite mining and processing has caused a pronounced impact both directly and indirectly on soils and ecosystems across large areas of the former GDR. We studied soils of pine forest ecosystems at sites affected by severe alkaline dust and sulphur deposition, stemming from lignite fired power plant emission, and at dumped sites from lignite mining. In this paper we summarize our main results and evaluate the long-term impact of lignite mining and combustion on the environment. The pine ecosystems on naturally developed soils show a clear effect of deposition history along a former deposition gradient with distinct changes in chemical properties of organic surface layers and mineral soil as well as in element turnover and cycling rates. Afforested sites on mining dumps are directly affected by the composition of the dumped substrates. Over a large area (800 km²) these substrates are dominated by Tertiary sediments with varying amounts of lignitic particles and pyrite that result in phytotoxic site conditions (pH < 3, high salt and metal contents). High amelioration doses of liming material (up to 200 t ha⁻¹) were applied for restoration purposes. We studied the development of these sites over a period of 60 years using a false-time series approach. Beside the extreme soil conditions, element budgets of these sites are characterized by very high element release rates over decades caused by pyrite oxidation and primary mineral weathering.     

尾矿库安全评价中的科学问题及评价方法探讨

尾矿库的安全稳定在矿山的安全生产和环境保护中具有十分重要的意义。尾矿库安全评价应该研究坝及其附属构筑物的安全状况，评价尾矿库的安全等级。本文立足于尾矿库工程的实践经验，探讨了尾矿库安全评价中应该涉及的科学问题，并对其相应的评价方法进行了探讨，指出了尾矿库安全评价应该采用的基于有限元理论的定量评价方法。本文认为排水不良和地震液化是影响尾矿坝稳定性的重要因素，应该在评价过程中给予重点的关注和研究。此外，在尾矿库的安全评价中，应更多地采用有限元数值计算方法研究上述科学问题。     

非饱和渗流作用下云阳西城滑坡稳定性分析

基于非饱和土理论采用有限元法模拟了云阳西城滑坡在雨水入渗和库水位下降过程中暂态渗流场的变化,然后将计算得到的暂态孔隙水压力分布用于滑坡稳定性的极限平衡分析。同时,采用延伸的摩尔—库伦破坏准则以便考虑基质吸力对抗剪强度的贡献,计算了暴雨工况和库水位下降工况下的稳定性系数。研究结果表明:降雨引起的暂态渗流场对滑坡稳定性有明显的影响;考虑基质吸力对抗剪强度的贡献,会明显提高滑坡稳定性;由于该滑坡渗透系数较大,库水位下降引起的暂态渗流场对该滑坡稳定性系数的影响不如降雨引起暂态渗流场的明显;该滑坡主要受暴雨影响。