周期排列水平管对地铁振动的隔振性能研究

根据声子晶体理论,提出了一种周期性排列的水平管隔振方法并探讨了其对地铁振动的隔振性能。利用平面波展开法与Bloch定理结合,得到水平管的能带结构。建立轨道?隧道?土体相互作用的三维ABAQUS精细化模型,进一步验证了周期性水平管对地铁振动的减振效果,并探究了水平管材料及其相关参数对隔振带隙的影响。结果显示：数值计算所得的衰减域与理论分析的带隙结果相吻合,周期性排列的水平管对特定频带的振动隔离效果明显且其隔振频带较宽。衰减域随填充材料弹性模量的减小逐渐下移;隔振频带的起始值随桩径的增大而提高;随着轴心间距的增大,衰减域上下限同时减小,同时也在一定程度上降低了整个隔振结构的带隙宽度。计算表明周期性水平管在不同参数条件下的频带范围在40～900 Hz之内。     

Dictionaries, disciplines and the future of geography

This essay contributes to the discussions initiated by Setten [Setten, 2008. Encyclopaedic vision: speculating on The Dictionary of Human Geography. Geoforum 39 (3), 1097–1104], about The Dictionary ofHuman Geography. Rather than focusing on the identity and relative exclusiveness of the contributors, I emphasize how successive editions of the Dictionary have helped reshape the discipline in two ways. First, the proliferation of texts, like the Dictionary, aimed squarely at a student market has gone hand in hand with a variety of changes to the political economy of publishing in geography. Second, human geography has increasingly come to be defined in terms of its concepts and theories. The paper ends by considering the implications of these changes for disciplinary unity and the future of geography given the increasing prominence of both of integrated environmental science and of GIS.     

模糊逻辑在物理栖息模拟中的应用

为了克服已有物理栖息地模型仅能在具有较完善监测资料河流使用的局限性,介绍了一种应用模糊逻辑的物理栖息地模拟方法。该方法以河道平面二维流场模拟结果为基础,将鱼类学和生态学专家的知识经验融入物理栖息地模型中,运用模糊逻辑推理计算栖息地各单元适宜度,最后根据加权可用面积、高适宜度面积比例与流量的关系曲线确定生态需水量。运用该方法对葛洲坝坝下中华鲟产卵栖息地进行模拟。研究结果表明,中华鲟产卵期适宜生态需水量为10 000~17 000 m3/s。分析认为该方法对监测资料依赖程度低,使用专家知识经验能够弥补数据不足造成的不利影响,具有一定的可行性及实用性。该研究有助于监测资料不足的河流开展生态保护及河流管理工作,并且能够为模糊数学理论在水生态学中的应用提供参考。     

Science and the St Elias: an evolving framework for sustainability in North America's highest mountains

The past, present, and future contributions of science in the St Elias Mountains, and its relationship with regional development, resource management, and traditional ecological knowledge is examined. Science has evolved from an early foundation of exploration, through stages of resource inventories and surveys, to deductive scientific research and, more recently, a promising reconnection with traditional knowledge. Directly and indirectly, events such as the Klondike Gold Rush, construction of the Alaska Highway, creation of the Arctic Institute of North America's Kluane Lake Research Station, and establishment of protected areas have helped foster scientific activities in the region. In turn, this scientific perspective has influenced regional development by providing detailed information that has been utilized, to varying degrees, in resource use, planning, and decisionmaking. Over the past decade, management of the region has become less sectoral and more cooperative in nature, due partly to the implementation of co-management agreements, regional land use planning, and settlement of first nations' land claims. Incorporating both science and traditional knowledge into this process through collaborative endeavours such as long-term ecological monitoring, adaptive management, and information integration will contribute to ecosystem-based management of the St Elias and ensure that both perspectives play an integral role in sustainable development of the region.     

Farmer-driven Innovation in New South Wales,Australia

Knowledge generation and the interactions that allow for knowledge exchange are key processes of innovation. Yet these processes are not well understood at the farm level, nor are they well reflected in policy approaches for agricultural innovation. Farmers in New South Wales have used diverse ways to implement innovations in land management. They employ a range of strategies including observing signals from the landscape, independent testing and trialling, use of agronomists, participation in farmer groups and in farmer-driven research programmes. Steps to foster farmer-driven innovations and knowledge-intensive agricultural systems require greater subtlety to enable flexibility, the incorporation of contemporary scientific knowledge and support for sustainable initiatives. More research on innovation and on policy engagement is required to foster on-farm innovative capacity.     

地学信息共享与知识发现

地学信息共享是地学研究的重要内容 ,也是地学 (数字地球 )发展的趋势之一。促使或完成地学信息共享的核心技术主要为技术标准化规范、空间数据库、互操作 (元数据 )以及传输信道技术等。知识发现是建立在共享的地学信息基础之上 ,能有效地实现知识的增值以及知识的再生。知识发现与信息共享二者共同促进 ,相互发展。     

不同土层地震反应计算程序对比分析

目前在中、美两国场地土层地震反应分析中,应用比较广泛的计算软件为ESE和SHAKE,两者均采用频域等效线性化方法处理非线性的土层动本构关系。本文采用上述软件分别对三种典型场地进行计算,分析两者差别及造成差别的原因。研究结果表明,SHAKE软件在深软场地时,计算反应谱和加速度峰值均与实际统计结果差别较大,不适合工程应用。ESE软件计算结果比较合理。     

层状大地频率域长导线源激发的电磁场

采用Fourier变换法从Maxwell方程组出发,导出了层状大地模型上接地长导线源激发的电磁场表达式。结果表明：接地长导线源实际上是2个接地电极和线电流源构成的一个组合源;其电磁场表达式表明平行于长导线方向的电场分量为2个接地电极激发的平行于长导线方向的电场分量和线电流激发的电场的叠加,垂直于长导线方向的电场分量和电场的垂直分量均是2个接地电极激发的;平行于长导线方向的磁场分量由2个接地电极所激发,而垂直于长导线方向的磁场分量为2个接地电极激发的垂直于长导线方向的磁场分量和线电流激发的磁场的叠加,磁场的垂直分量为线电流源所激发。进一步的结果分析表明,在均匀半空间上、大收发距时,2个接地电极激发的平行于长导线方向的电场分量和线电流激发的电场分量是相等的,2个接地电极激发的垂直于长导线方向的磁场分量和线电流激发的磁场分量是相等的,且它们的振幅与2个电极之间的距离成正比。     

井间地震时频域联合速度和衰减系数同步层析反演

井间地震资料中蕴含丰富的地下储层岩性和物性信息,利用井间地震直达波初至信息,通过层析反演可以得到两井之间的速度剖面。通过对井间地震直达波振幅衰减信息的处理,可以实现井间的吸收衰减层析成像。基于井间地震直达波射线路径的一致性,提出了井间地震时域直达波走时层析反演和频域质心频率衰减层析同步反演方法,增加了约束条件,增强了抗干扰能力。对模型和实际资料的处理结果表明,速度和吸收衰减同步反演方法,提高了速度层析反演精度,得到了对油气更为敏感的衰减属性,增强了井间地震在储层描述和油气预测中的应用能力。