Group velocity of anisotropic waves—Part I: Mathematical expression

The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition for deriving the mathematical form of group velocity, because it cannot specify a unique direction in which wave energy or crests propagate. The derived mathematical expression is available only for isotropic waves. But for anisotropic waves, the traditional group velocity may have no a definite direction, because it varies with rotation of coordinates. For these reasons, it cannot be considered as a general expression of group velocity. A ray defined by using this group velocity may not be the trajectory of a reference point in an anisotropic wave train. The more general and precise expression of group velocity which is applicable for both isotropic and anisotropic waves and is independent of coordinates will be derived following the displacement of not only a wave envelope phase but also a wave reference point on the phase.     

3G技术4D集成在云南边防信息系统中的应用

讨论了 4D集成的空间数学框架、空间与非空间数据库组织方式、数据模型设计以及 3G技术结合的可能性与可行性 ,并介绍了其在云南边防信息系统中的集成及应用情况。     

GML空问数据存储映射模型研究

提出了一种将GML文档存储到空间数据库的存储映射模型G2SDB ,同时通过定义边表 ,保留GML文档的部分结构信息 ,有利于处理GML查询中的路径表达式 ,提高查询操作的效率 ,也有利于GML文档的重构。     

安阳区域性夏季大旱成因分析

利用1957～1998年安阳区域夏季降水资料，确定安阳区域性夏季大旱的标准，分析了大旱成因：东亚沿海低槽较常年异常深厚和偏东以及西太平洋副高异常偏东、偏南和偏弱；当年6～8月太阳黑子相对平均数处于谷点或从谷点开始上升时期；当年春季出现厄尔尼诺或存在厄尔尼诺现象，绝大部分安阳降水偏少或特少，出现干旱或大旱；6～8月西风急流轴异常偏北，也是造成安阳区域性夏季大旱的原因之一。     

Isotope Dilution MC-ICP-MS Rare Earth Element Analysis of Geochemical Reference Materials NIST SRM 610, NIST SRM 612, NIST SRM 614, BHVO-2G, BHVO-2, BCR-2G, JB-2, WS-E, W-2, AGV-1 and AGV-2

We present data for the concentrations of eleven rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, Yb, Lu) in eleven international geochemical reference materials obtained by isotope dilution multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). We have analysed both rock powders and synthetic silicate glasses, and the latter provide precise data to support the use of these as reference materials for in situ trace element determination techniques. Our data also provide precise measurements of the abundance of mono-isotopic Pr in both glasses and powders, which allows more accurate constraints on the anomalous redox-related behaviour of Ce during geochemical processes. All materials were analysed in replicate providing data that typically reproduce to better than one percent. Sm/Nd ratios in all these materials also reproduce to better than 0.2% and are accurate to < 0.2% and can thus be used as calibrants for Sm-Nd geochronology. Our analyses agree well with existing data on these reference materials. In particular, for NIST SRM 610, USGS BHVO-2, AGV-1 and AGV-2, our measured REE abundances are typically within < 2% (and mostly 1%) of REE concentrations previously determined by isotope dilution analysis and thermal ionisation mass spectrometry, consistent with the higher degree of precision and accuracy obtained from isotope dilution techniques. Close agreement of results between basaltic glass reference materials USGS BHVO-2G and BCR-2G and the BHVO-2 and BCR-2 powders from which they were created suggests that little fractionation, concentration or dilution of REE contents occurred during glass manufacture.     

基于地学G~4I系统的元数据分类方法

以实现空间数据的标准化为前提,对空间数据库中元数据管理系统的作用和分类原则进行了探讨,指出了传统的分类方法对于以矿产资源预测为目标的地学系统而言存在着弊端。需要结合矿产资源预测的特点,对空间数据库建设中元数据的分类原则进行补充,提出了面向客户应用即按矿产资源预测目标进行分类,实现对空间数据查询的高效利用。该方法可以在地学G4I系统中得以实施和应用。     

孔压静力触探(CPTU)测试成果影响因素及原始数据修正方法探讨

孔压静力触探(CPTU)是20世纪80年代在国际上兴起的新型原位测试技术,因其诸多优点,目前在欧美诸国已得到广泛应用。由于探头规格、技术标准和操作程序的差异,影响CPTU测试成果的因素很多,而且其影响程度也各不相同。根据前人的研究成果,对CPTU测试成果的影响因素进行了分析总结,以期在CPTU资料整理和应用中引起重视。最后,简要论述了考虑诸多影响因素的原始数据修正方法。     

A VLBI Delay Model for Radio Sources at a Finite Distance

A relativistic delay model for Earth-based very long baseline interferometry (VLBI) observation of sources at finite distances is derived. The model directly provides the VLBI delay in the scale of terrestrial time. The effect of the curved wave front is represented by using a pseudo source vector K = (R ₁ + R ₂)/(R ₁ + R ₂), and the variation of the baseline vector due to the difference of arrival time is taken into account up to the second-order by using Halley’s method. The precision of the new VLBI delay model is 1 ps for all radio sources above 100 km altitude from the Earth’s surface in Earth-based VLBI observation. Simple correction terms (parallax effect) are obtained, which can also adopt the consensus model (e.g. International Earth Rotation and Reference Frames Service conventions) to finite-distance radio source at R > 10 pc with the same precision. The new model may enable estimation of distance to the radio source directly with VLBI delay data.     

方差分量的极大验后估计

由概括函数模型出发,导出了适应于所有平差模型的方差分量的极大验后估计,这种估计实际上是先验方差与样本方差的凸组合。文中还给出了一个简单的数例,说明这种方法的可行性。     

第29届IASPEI大会岩石圈结构,动力学过程和各向异性专题概述

第２９届ＩＡＳＰＥＩ大会于１９９７年８月１８～２８日在希腊塞萨洛尼基举行,来自世界各地的约１０００名科学家出席了本届大会。该文较详细地介绍了本届大会中有关“岩石圈结构、动力学过程和各向异性”专题（Ｓ１１）的学术交流情况及各国学者在该专题的研究方面所取得的进展。