A high‐resolution pollen and geochemical analysis of late Holocene human impact and vegetation history in southern Cumbria,England

The historic era, which in Cumbria begins with the Roman invasion of AD 71, is a frequently neglected period in palaeoecological research, but its study can bring benefits in improving knowledge of landscape history and in understanding the significance and limitations of palaeoecological records. Pollen and geochemical data are presented for late Holocene records from Deer Dyke and Hulleter Mosses in southern Cumbria. The records show initially low levels of anthropogenic impact, followed by a phase of forest clearance and mixed agriculture from the 7th to 11th centuries AD. The timing of these clearances suggests that they were initially Anglo‐Saxon in origin, rather than Norse. Further clearances in the 16th century AD are interpreted as a response to monastic dissolution and late Tudor population pressures; the landscapes reached their contemporary form following extensive clearances in the 17th century AD. Silicon and titanium concentrations at Deer Dyke Moss were used to reconstruct past levels of atmospheric dust loading, which is broadly related to soil erosion. Geochemical influx was found to peak during periods of landscape transition rather than from established land use. This relationship with pollen data is thought to reflect the predominantly low levels of anthropogenic impact in the region, which changes as substantial woodland clearances during the 16th century AD and continuous land use pressure since then have greatly increased the supply of airborne dust. Copyright © 2008 John Wiley & Sons, Ltd.     

Elasto-Plastic Analysis of Tubular Joints of Offshore Platforms by Finite Element Method

The plastic node method is reformulated by the variational principle and is applied to elasto-plastic finite element analysis of tubular joints, eventually including the effect of internal and external gussets, stiffener rings, etc., if necessary. Four different joints are studied here in detail for the elasto-plastic behavior, the strain at the hot spot, the strain concentration factor around the intersection line, and the propagation of the plastic region with loading up to collapse in order to determine the ultimate strength, safety factor, and development of the plastic field. The present results are in good agreement with the experimental results.     

江西省永平铜矿西部排土场极限堆载高度确定

国内外对排土场极限堆载高度的理论计算缺乏研究,目前尚无成熟的统一理论计算方法。文章结合永平铜矿西部排土场的工程实例,在进行边坡工程地质条件勘察与排土场岩土物理力学性质试验研究的基础上,采用数值计算方法对排土场进行了分层堆载数值模拟计算。通过对计算结果的分析,得到位移、塑性区与安全系数随堆载高度的变化规律,并确定了该排土场的极限堆载高度。     

RUSLE及其影响因子的快速计算分析

RUSLE是目前应用最广泛的土壤侵蚀模型。虽然是一种经验模型,但是其影响因子计算仍然非常复杂,满足不了区域土壤侵蚀的快速提取要求。针对这种状况,文章在介绍RUSLE手册中每个影响因子计算方式基础上,分析总结了可进行快速计算的方法,实验表明,采用文章推荐的因子计算方式,可达到快速有效的目的。     

Climate changing characteristics of Zhangye City in Heihe River basin during 1968–2005

At present, researches on climate change of the Heihe River basin mainly focus on the relationship between basin climate change and regional water resources, regional desertification and dynamic climatic seasons of sandstorm, but less on climate change of oasis region, where there are more intense and frequent human activities. Based on data of precipitation, temperature, strong wind and dust events frequencies obtained from the six meteorological stations of Zhangye region in Heihe River basin, the features of climate change during 1968–2005 were carefully studied. Results show that the regional temperature rise rate exceeded the average level of China. The annual precipitation changed a little, but the precipitation had a slowly increasing trend in spring and winter. Frequencies of strong wind and sandstorm days show obviously descending trends, which had a close correlation with the regional temperature rise and the precipitation increase in spring and winter. Meanwhile, further human economic activities and exploitations to the oasis in the inland valley of arid regions also affected the climate change of this region, which has a sensitive and fragile eco-environment. __________ Translated from Journal of Desert Research, 2007, 27(6): 1048–1054 [译自: 中国沙漠]     

绿色建筑的内涵及其发展的若干思考

随着我国城市化进程的快速推进,大规模的人居环境建设使我国的资源与环境面临巨大的挑战,发展绿色建筑已经成为可持续发展的重大战略问题.文章从可持续发展的角度,指出了绿色建筑的内涵与特征,并归纳了绿色建筑与一般建筑的区别.在此基础上,提出了发展绿色建筑的具体对策.     

江西瑞昌1995年ML4.9级地震前后九江地震台倾斜固体潮汐变化分析

通过月整点值数据文件和滑动值数据文件这两种数据处理形式。对九江台地倾斜资料进行调和分析计算。分析了M2潮汐因子与瑞昌ML4.9级地震的关系。认为存在震前短临异常或震后异常，并与趋势异常得到相互印证。     

人类活动对黄河中游高含沙水流的影响

以黄河中游干流和渭河、无定河的资料研究了人类活动对黄土高原河流高含沙水流的发生频率的影响。人类破坏森林植被，大量拦截黄河上游清水来源区的清水基流，使得高含沙水流发生频率增大，大规模水土保持措施的实施则使高含沙水流发生频率迅速减小。近50年来黄河干流和一些支流的高含沙水流随时间的变化可以用一个三阶段模式来概括，即20世纪50-60年代，由于人类破坏植被，使高含水流频率增大；20世纪60年代末至80年代中期，大规模水土保持措施的实施使高含沙水流发生的频率减小；20世纪80年代末期以来，人类大量拦截利用清水资源，使高含沙水流的发生频率又复增大。