碟形弹簧竖向减震体系的分析与研究

对碟形弹簧竖向减震体系利用时程分析方法对其进行动力分析，并输入不同场地、不同频谱的地震波考察其减震效果，验证了碟形弹簧在合理控制其刚度的前提下可以起到有效减小竖向地震的作用。     

液化土层对地表加速度反应谱的影响

采用一种改进的有效应力方法研究土层液化对地表加速度反应谱的影响，分析中考虑了砂层的厚度、埋深和输入地震波的幅值和波型等因素。分析结果表明，土层液化使地表加速度反应谱的特征周期至少延长0．1秒以上，使原Ⅱ类场地变为Ⅲ类场地，高烈度时易变成Ⅳ类场地，反应谱中周期0．8秒-1．0秒是液化砂层加震或减震的一个分界点，液化对反应谱短周期分量具有一定的减震作用，而对长周期分量有非常显著的放大作用。     

巴楚-伽师Ms6.8地震地磁异常特点分析

通过分析、比较1996--2003年喀什地震台站记录到的新疆伽师及附近地区发生的多次6级地震的地磁前兆异常特征，发现在这几组地震活动过程中喀什地震台的地磁表现出不同的异常特征，说明与地震破裂特征有更深层次的相关性，且地磁响应比异常和总强度差值异常在一定程度上反映了台站周围小范围的震源区介质电性结构的变化。巴楚-伽师6．8级地震前地磁异常特征并不十分突出，有别于1996—1998年伽师强震群震前地磁异常量较丰富的特点。     

Vicissitude of Sogo Nur and environmental-climatic change during last 1500 years

Lakes in arid zone are sensitive to climatic changes. The lacustrine sediment sequence in Sogo Nur has well and truly recorded climatic events such as the Sui-Tang Dynasty Warm Period, the Song-Liao Dynasty Cold Period, the Medieval Warm Period, the Little Ice Age and the 20th Century Warm Period. Commonly, the climate in warm Periods was relatively humid,accordingly the lake area extended and water level rose, and vice versa. Apart from climatic change, human activity is also an important factor of influencing lake vicissitude, and they played the dominant role alternatively during different periods; the factor of climatic change predominated in historical period, while since the beginning of the 20th century the utilization of water resources by human has became decisive.     

Rainfall thresholds for landsliding in the Himalayas of Nepal

Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to three orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 years of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure.     

A 3D BEM-FEM methodology for simulation of high speed train induced vibrations

This work presents an efficient methodology for the analysis of vibrations in a railroad track system, induced by the passage of conventional and high-speed trains. To this end the Boundary Element Method is used to model the soil-tie system within the framework of impulse response techniques. Conventional Finite Element Methods along with Newmark's integration is used for the modeling of the rail system. The two methods are coupled at the tie-rail interface and the solution is obtained following a staggered, time marching scheme in an efficient manner. The methodology accounts for Soil-Structure Interaction and traveling wave effects. In addition, this work identifies the parameters that affect the efficient modeling of railroad track systems as they pertain to the proposed solution methodology.     

GM4型磁通门磁力仪性能检验方法

目前,磁通门磁力仪广泛应用于观测地球磁场相对变化的仪器。相对于应用,仪器的性能测试不为人们所熟悉。本文针对GM4型磁通门磁力仪的噪声特性,频率特性,线性度,温度特性等关键性能指标的测试依据、测试方法及流程给予详细的阐述。     

黄河流域气候水分盈亏时空格局分析

以中国气象局整编的1961~2001 年的气象资料为数据基础,采用联合国粮食及农业组织(FAO)1998 年推荐使用的Penmanmonteith模型,并以GIS技术为手段进行黄河流域气候水分盈亏的时空分布格局分析。结果表明：黄河流域干旱缺水是一种普遍现象,气候水分盈亏量在空间上总的变化规律表现为自南向北、自东向西气候水分亏缺量呈逐渐增大趋势,大部分地区全年气候水分亏缺量介于200~600 mm之间;就季节分布而言,水分亏缺的主要时期在春季和初夏,亏缺量一般在180~300 mm之间;就典型站点气候水分盈亏量逐月变化而言,存在着区域差异。研究结果和结论对区域充分发挥水分利用效率、发展高效节水农业具有重要意义。     

1948～2004年全球越赤道气流气候变化

利用1948年1月～2004年12月逐月NCEP/NCAR的全球1000 hPa、850 hPa、700 hPa、600 hPa、500 hPa、400 hPa、300 hPa、200 hPa、150 hPa、100 hPa的10层经向格点风,计算了全球越赤道气流和年变化,分析了全球850 hPa越赤道气流通道的时、空变化特征。指出在研究的时间段内,全球850 hPa越赤道气流有明显的长期趋势变化和年代际变化。近57年,6～8月的45～50°E、5～9月的105～115°E、5～9月和5～11月的130～140°E、2～4月的20～25°E的越赤道气流有明显的加强,6～8月的50～35°W的越赤道气流减弱。夏季索马里的越赤道气流,平均每10年增强0.25 m/s,而130～140°E,5～9月的越赤道气流,平均每10年增强0.32 m/s。奇异谱分析表明,850 hPa越赤道气流的年代际变化和趋势变化的方差贡献达到35%～45%。年际变化的方差贡献不超过30%,还指出夏季太平洋的越赤道气流的强度变化与南方涛动有明显关系,弱南方涛动时,有强的越赤道气流。而索马里急流强度与北大西洋涛动有弱的正相关。     

黄河上游地区气候变化及其对黄河水资源的影响

通过对1961年以来黄河上游地区气候变化的分析,发现黄河源区进入80年代中后期以后,年平均气温上升趋势非常明显,特别是1998年的年平均气温竟达到-2.1℃,是40年来年平均气温最高的一年;进入90年代,春季和夏季温度急剧回升.黄河上游地区年平均降水量及秋季降水量无明显的变化趋势,且其年际间的波动趋于缓和;冬季(12～2月)和春季(3～5月)降水量的变化趋势呈现出逐年增多的趋势;夏季(6～8月)降水量变化趋势却表现出显著的减少趋势.同时,分析了38年黄河上游径流量及其与流域降水、气温的关系,着重分析了干旱气候对黄河水资源的影响.结果表明,黄河上游地区水资源呈减少趋势,其减少趋势进入90年代后尤为明显.这一变化趋势与黄河上游地区夏季降水量变化趋势有着一致性,说明汛期降水量的减少是黄河上游流量减少的最直接的气候因子.