昆仑山口西地震激发的地球环型振荡

利用中国数字地震台网(CDSN)改造后的7个台站3天的VHE、VHN波形资料,采用功率谱密度估计方法,在没有对资料进行去固体潮处理的情况下,提取了2001-11-14昆仑山口西地震激发的0T2～0T40地球环型自由振荡,并与地球初步参考模型(PREM)的理论自由振荡周期进行对比,发现环型振荡振型周期与PREM预测的环型自由振荡周期符合得很好。频率与PREM模型略微不一致的环型振荡振型可以解释为地球介质的横向不均匀性和各向异性所致。因此地球自由振荡信息可用于揭示地球的三维不均匀结构信息或各向异性信息,并可能对区分地幔对流模式(全地幔对流或上地幔对流)有所帮助。     

Spatio-temporal analysis of alpine ecotones: A spatial explicit model targeting altitudinal vegetation shifts

There is general agreement in literature that Alpine vegetation belt ecotones have shown a trend of upward migration in the last few decades. Despite the potential of such shifts as indicators of global change effects in mountain ecosystems, there are relatively few works focused on their assessment in a systematic and spatially explicit way. In this work our aim is to quantify the altitudinal shifts and analyse the spatial pattern dynamics of mountain ecotones. We developed a novel procedure to delineate the current and former state of three characteristic mountain ecotones, which we formalised as forest, tree and tundra lines. Our approach is based on the recognition of altitudinal extreme outposts identified with ecotone locations at a slope scale. The integration of multi-temporal datasets allows the identification and quantification of altitudinal advances and retreats in the outpost locations for a given period. We tested the method in a section of the Italian Alps for the period 1957-2003. Results show a general trend of an increase in altitude for the three ecotones, despite the occurrence of occasional decreases. We estimate decadal altitude increments of 25 m for forest line, 13 m for treeline and 11 m for tundra line. We also identified changes in ecotone spatial morphology between the two dates, with significant implications in connectivity and colonisation dynamics.     

高原多年冻土区隧道暗挖法安全稳定性三维数值分析

青藏铁路风火山隧道以其高海拔、常年冻土环境而给施工带来了新的挑战 ,为了防止土体冻融产生的冻胀力对隧道结构造成的破坏 ,施工中必须强调衬砌结构的快速封闭。虽然全断面法和微台阶法均能较快地实现衬砌的封闭 ,但在洞口段岩体较为破碎的条件下 ,到底哪种方法能够满足既安全又快速的施工要求 ,是摆在施工者面前的难题。笔者采用三维数值模拟的方法 ,对风火山隧道出口端的开挖方法和支护方式的安全稳定性进行了研究 ,其结果认为 ,全断面开挖难以控制工作面的稳定 ,会因过大沉降和结构开裂而危及施工安全 ,而同等条件下 ,采用微台阶法施工 ,则可以将拱顶沉降和结构应力控制在允许范围内。经分析对照 ,证明数值分析预测结果正确 ,与施工实践有很好的一致性。     

A mathematical structure for analyzing maps

The growing use of computers in environmental management is profoundly changing data collection procedures, analytic processes, and even the decision-making environment itself. The emerging technology of geographic information systems (GIS) is expanding this revolution to integrate spatial information fully into research, planning, and management of land. In one sense, this technology is similar to conventional map processing involving traditional maps and drafting aids, such as pens, rub-on shading, rulers, planimeters, dot grids, and acetate sheets for light-table overlays. In another sense, these systems provide advanced analytic capabilities, enabling managers to address complex issues in entirely new ways. This report discusses a fundamental approach to computer-assisted map analysis that treats entire maps as variables. The set of analytic procedures for processing mapped data forms a mathematical structure analogous to traditional statistics and algebra. All of the procedures discussed are available for personal computer environments.