Functional substitution of coordination polyhedron in crystal structure of silicates

On the bases of the study of comparative crystal chemistry of silicates it has been concluded that the octahedra and square pyramids of Ti-0 and Zr-0 play functional role of tetrahedra of Si-0 in the construction of crystal structures. Therefore, those silicates may be named titano-and zircono-silicates. Because of the functional similarity of coordination polyhedra, the structures of cristobalite and feldspar have been compared with those of perovskite and garnet, respectively. As a new concept, the functional replacement of tetrahedra by octahedra and/or pyramids is defined by the authors of this paper for favorable comparison of relative crystal structures.     

Environmental records of carbon in recent lake sediments

Based on careful sampling and accurate analysis of recent sediments in Lake Chenghai, this paper discusses the staggered positive/negative correlation between organic carbon (OC) concentration and inorganic carbon (IC) concentration. The result indicates that temperature change, and its induced relative changes are the main factors affecting the relationship between IC concentration, δ¹³C of carbonate and OC concentration. When temperature and its induced photosynthesis strength change control autochthonous calcite precipitation, OC concentration is positively correlated with IC concentration and δ¹³C of carbonate. When temperature and its induced physical/chemical changes dominate, OC concentration displays negative correlation with IC concentration and δ¹³C of carbonate. IC concentration and δ¹³C of carbonate in sediments of Lake Chenghai are good proxies for climatic warm/cold changes.     

Methods to determine storativity of infinite confined aquifers from a recovery test

Starting from the equations of Theis and Cooper-Jacob, two new mathematical methods are proposed for interpreting the residual drawdown data for an infinite confined aquifer. Under Theis' assumptions and using the Cooper-Jacob approximation, the principal aquifer characteristics of transmissivity, pumping storativity, and recovery storativity are expressed without any correction or additional assumption. An actual case is used for illustration and confirms the validity of proposed equations and methods.     

多区域海洋M3分潮的观测与验证

M₃海洋分潮(三阶潮或一日三次周期潮汐)经常受到忽视,因而对M₃分潮进行更精确的分析研究,可以提高潮汐预测、海洋数值模拟、大地测量的准确度.尽管M₃分潮在整体潮汐所占比例较小,但由于陆架共振及其他影响,某些沿海地区M₃潮可大大增强.本文使用157个验潮站的数据,以及9年时间窗口,对水位变化进行了潮汐谐波分析.本文还分析了太阴M₃潮,将这些结果与全球同化的模型数据(TPXO9v5a)进行了比较,重点研究了西太平洋和欧洲陆架地区.与验潮站数据相比,大部分区域TPXO9v5a导出的M₃潮振幅和相位滞后表现良好,但在沿海和地形复杂的区域,其结果误差较大.在欧洲陆架海域使用了一个浅水数值模型(MARS),该模型在某些地区优于TPXO的结果.在欧洲陆架海域的五个子区域中, TPXO在三个地点的M₃振幅及相位滞后预测的均方根误差(RMSE)更小.而在其他子区域, MARS模拟结果更为准确.本文发现一些地点的M₃振幅有着显著长周...     

HYDRODYNAMIC MODELLING OF ESTUARINE CIRCULATION USING A SPLINE METHOD OF FRACTIONAL STEPS

I. INTRODUCTIONNumerical models of estuaries incorporating simulation of the density induced circulation are consideredimPOrtant tools in the assessment of their dispersive characteristics. Most models to date have used finite difference approximations to the governing equations (see for example thericke and Hogan, 1977, Blumberg,1 977, Perrels and Karelse, 1978). A numeriCal model of estuarine circulation using a SADI (Spline Alternating Direction implicit) procedure together with a…     

运用声纳信号估算2004年12月26日苏门答腊特大地震的破裂长度和速度

位于印度洋由5个小声纳台阵构成的台网无先例地记录到了与2004年12月26日苏门答腊特大逆断层地震相关的声纳信号，这些声纳台阵距离震中约2800～7000km。每个台阵都记录到由这次地震产生的声波（也称为T波）。通过在T波尾波持续时间内用短时间窗分析后表明，作为时间函数的源方位角接收器变化缓慢。这一分析也表明了视T波波源并不是静止的。视T波波源以2km／s的平均速度沿着巽他海沟向北移动，与这次地震的破裂轨迹很相似。声纳数据说明了地震破裂过程明显地分为2个阶段，刚开始是以大约2．4km／s沿着巽他海沟朝西北方向破裂。到了距离震中600km附近破裂速度下降至大约1．5km／s，但仍朝着西北继续扩展。     

1976年中国唐山地震序列的应力相互作用

研究了1976年中国唐山Ms7．8级地震两个主震事件和两个最大余震之间的静态应力相互作用。断层参数取自前人大地测量和远震波形反演结果。对于序列中的每个事件，我们计算了前面所有事件产生的包括孔隙压力变化的库仑破裂应力（CFS）变化。我们发现，在所有情况下，对于最优的力学参数得到的增加的库仑应力变化几乎涵盖了有关的整个断层。我们认为，应力相互作用在确定主震以外地区中何处可能发生大余震是很重要的。快速确定主震位置和机制，并结合对附近主要断层的认识，对后续事件的危险性评估是有用的。