澳大利亚奥林匹克坝铜-铀-金矿床

澳大利亚奥林匹克坝矿床以铜、铀为主,铜品位约为2～3%,铀0.5～1.5公斤/吨,矿区面积20平方公里,矿化垂直厚度从几十至数百米,矿石储量尚待发表.此外,还有相当含量的稀土、金和银.该矿床位于阿得雷德西北约650公里的洛克斯比当斯牧场一带(图1).这里地势平缓,有砂丘和一些粘土盆地,是在上元古代和寒武纪沉积物上发育形成的.     

Population trends of Soviet cities, 1970-84

This article contains a time series for the population of cities of the Soviet Union for the period 1970-1984. The data are from the Soviet censuses of 1970 and 1979 and from official estimates for 1974 and 1984. The article is designed as a continuation of an earlier time series developed by Chauncy D. Harris for the period 1897-1967. "The updated material consists of a series of tables following the patterns of the earlier material, a methodological explanation, and a discussion of significant trends in the population size of Soviet cities."     

八十年代地图学的大变革

地图学正处于变革阶段。在其发展史上,这门学科从未在数据获取方法上经历过如此急剧的技术进步,而同时在生产技术方面也正经历着如此戏剧性的进步。在过去,常常通过技术革新来获得数据集,例如,土地测量精度的提高应归于欧洲文艺复兴前阿拉伯地图学家运用数学方法的进展;海上测量精度的提高也是18世纪以来航行表的发明和系统调查方法采用的结果。在另一时期,地图生产新技术随着印刷、照相、塑料的发明等技术变革而发展。然而,今天地图工作者正同时经历着     

萤石矿化的Sm—Nd直接测年法

业已证明，直接测定许多热液矿化类型的年龄是困难的，因而限制了人们对促使地壳流体流动和主要矿床形成的地质作用的了解。同一条脉体中热液矿物萤石在稀土元素丰度和Sm/Nd比值方面表现出了相当大的变化。我们对英格兰西南部以花岗岩为主岩的典型锡矿床中的萤石进行了Sm-Nd年龄测定，证明了Sm-Nd测年法是精确的矿化计时计。萤石中轻稀土元素含量有着相当大的变化，而且认为富轻稀土元素矿物相的同时沉淀可能是引起Sm/Nd比值变化的原因。     

A theoretical test of the geostrophic momentum approximation

A previously developed model of a 2-dimensional air flow with constant horizontal shear is used to estimeate the accuracy of the geostrophic momentum approximation by comparison of exact solutions when exist with approxi-mate ones.     

ON ICE FORMING NUCLEI

Cloud condensation nuclei(CCN)constitute a reservoir of latent ice-forming nuclei(IFN)active by condensation-followed-by-freezing and by sorption.Two classes of aerosol particles active as IFN by sorption werefound.The first produces IFN concentrations which are dependent on temperature only.The IFN concen-tration consecutively increases with lowering of temperature and does not respond to the increasing partialwater vapor pressure.The second produces IFN concentrations which are dependent on partial water vaporpressure only,The IFN concentration consecutively decreases with decreasing of the partial water vapor pres-sure that takes place with the lowering temperature.Sulfates(mostly ammonium sulfate)constitute an integral part of IFN active by condensation-followed-by-freezing and by sorption.Backward isentropic air parcel trajectories linked polluted air rich in sulfates andclean air with high and low concentrations of IFN active by condensation-followed-by-freezing at-19.7℃ andS_w=0.1%.The experiments were performed in a dynamic filter processing chamber with aerosol particles collectedon membrane filters.     

降水概率的业务含义

自从降水概率(POP)在国家天气服务(NWS)预报中出现,对于预报员和用户来说,深刻理解降水概率意义的细微差别是非常重要的.本文简述了POP理论.尽管POP定义为平均点概率,但国家天气服务业务手册(NWSOM)中将POP解释为降水复盖面积除以预报面积的期望值.     

梅雨锋及其低空急流的数值模拟

使用二维锋面模式研究了东亚梅雨锋的结构与特征,并讨论了湿度和地面通量对梅雨锋的影响及其有关的低空急流。