A critical state model for sands dependent on stress and density

An elastoplastic model for sands is presented in this paper, which can describe stress–strain behaviour dependent on mean effective stress level and void ratio. The main features of the proposed model are: (a) a new state parameter, which is dependent on the initial void ratio and initial mean stress, is proposed and applied to the yield function in order to predict the plastic deformation for very loose sands; and (b) another new state parameter, which is used to determine the peak strength and describe the critical state behaviour of sands during shearing, is proposed in order to predict simply negative/positive dilatancy and the hardening/softening behaviour of medium or dense sands. In addition, the proposed model can also predict the stress–strain behaviour of sands under three-dimensional stress conditions by using a transformed stress tensor instead of ordinary stress tensor. Copyright © 2004 John Wiley & Sons, Ltd.     

Sedimentary cycles of trace elements in Salawusu River Valley since 150 ka BP

The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results show that the content and variation of trace elements has experienced remarkably regular changes in the pace with coarse and fine sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The trace elements with chemical properties of relatively active (V, Sr, Cu, Ni, As) and relatively stable (P, Pb, Rb, Mn, Nb, Zr) are a manifestation of the corresponding 27 changeable cycles between peak and valley values, appearing a multi-fiuctuational process line of relative gathering and migration since then. The low numerical value distribution of these two types of trace elements in the aeolian sand facies represents erosion and accumulation under wind force during the cold-dry climate. Whereas their enrichments in both fluvio-lacustrine facies and palaeosols are related to the valley’s special low-lying physiognomic position between the Ordos Plateau and the Loess Plateau under the warm and humid climate conditions. The above relatively migrated and gathered change of the trace elements is the result of 27 climatic cycles of cold-dry and warm-humid, which is probably caused by repeated alternations of winter monsoon and summer monsoon in the Mu Us Sandy Land influenced by the climate vicissitudes in northern hemisphere during glacial and interglacial periods since 150 ka BP.     

山西省主要河流流域面雨量预报业务流程

以T213、HLAFS模式、MM5中尺度模式输出的格点资料以及日本降水量格点资料为基础，将影响山西降水的天气动力模型归纳为诊断模型，从中引出多个能够全面反映降水模型特征的综合物理因子；根据各种数值模式输出的降水量预报性能和质量优劣特点，依据数值模式的形势场预报优于要素场预报的现实，构造在不同环流形势背景下，启动不同预报方程的面雨量预报业务流程，有效地遏止了在环流形势调整时预报输出不能快速响应的弱点，提高了点和面雨量预报的准确度。     

我国地震预报的战略建议与思考

讨论了我国地震预报面对的问题和困难。认为只有加强以形变为主的前兆观测 ,才能作出地震的短临预报。目前前兆观测的主要问题在于可信度差 ,应把重点放在仪器探头上 ,只有探头提供的信息“源”可靠了 ,后续的采集、传输、预报的“流”才会有坚实的基础。我国现在建立以形变为主的前兆台网的技术条件已经成熟 ,建议建立全国高精度的高、中、低频衔接的前兆物理信息观测网络。     

水库流域体积降水量预报方法研究

根据广东飞来峡水库流域汇流特征,将全流域划分为5个支流,并采用求积仪分别计算各支流面积;然后用加权平均法计算各支流的面雨量,并将各支流面雨量对相应的支流面积进行积分,计算各支流体积降雨量;利用洪水过程飞来峡水库入库流量、出库流量和水库流域蒸发量对体积降水量预报结果进行验证,求出误差订正系数.结果表明:利用加权平均法计算的水库流域体积降水量,经过误差订正后,预报准确率可控制在90%左右,基本满足预报业务服务要求.     

四川那朗地区多金属矿化地质及激电特征

四川那朗地区地处三江成矿带,区内出露三叠系灰岩、板岩及火山岩,有闪长岩岩株侵入其中,地表见铁帽。岩体蚀变分带明显。通过激发极化法工作,由视极化率处理后异常显示,原始数据圈出了激电异常,推测为铁帽下部之矿（化）致异常。     

具有随机状态转移矩阵的Kalman滤波

讨论状态转移矩阵为随机性矩阵时的Kalman滤波方法,并给出滤波的具体算法及分析滤波的收敛特性和参数的取值范围。通过实际算例证实了该滤波方法的有效性。     

海洋古生产力重建初探──以南沙群岛海区NS90-103柱样为例

以南沙海区ＮＳ９０－１０３柱样为例，利用各种古生产力指标物，如有机碳含量，有孔虫壳和有孔虫碳同位素，重建了２０００００ａ以来古生产力变化，并对结果予以讨论。     

WATER RESOURCES TRANSFORMATION AND WATER QUALITY VARIATION IN THE URUMQI RIVER BASIN

ＷＡＴＥＲＲＥＳＯＵＲＣＥＳＴＲＡＮＳＦＯＲＭＡＴＩＯＮＡＮＤＷＡＴＥＲＱＵＡＬＩＴＹＶＡＲＩＡＴＩＯＮＩＮＴＨＥＵＲＵＭＱＩＲＩＶＥＲＢＡＳＩＮＱｕＹａｏｇｕａｎｇ（曲耀光）；ＬｕｏＨｏｎｇｚｈｅｎ（骆鸿珍）（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＧ...