金伯利岩,钾镁煌斑岩中含大阳离子复杂钛酸盐矿物晶体结构特征

近年来，在我国山东蒙阴及南非，西北澳大利亚的金伯利岩，钾镁煌斑岩等地幔岩中陆续发现了一系列新的钛酸盐矿物，包括蒙山矿系列，沂蒙矿系列，柱红石系列，钾钡石及易解石类矿物新种，它们分别具ＡＭ２１Ｏ３８，ＡＭ１２Ｏ１９，Ａ１－２Ｂ８Ｏ１６，Ａ２Ｂ６Ｏ１３，ＡＢ２Ｏ６等化合物的结构，其共同特征是含亲石大阳离子及硅酸盐不相容元素。笔者通过对其中一些矿物的晶体结构测定，综合国内外的有关资料，指出大阳离子在这些     

Determining elastic constants of transversely isotropic rocks using Brazilian test and iterative procedure

The elastic constants of rocks are the basic parameters for rock mechanics, and play a very important role in engineering design. There are many laboratory methods to determine the elastic constants of transversely isotropic rocks, and the Brazilian test is a popular method. This paper presented a method combination of the Brazilian test, back calculation, and iterative procedure to evaluate the five independent elastic constants of transversely isotropic rocks in laboratory. The strain data at the centre of discs were obtained using Brazilian test. The stresses at the centre of discs were computed using numerical programs. By using back calculation, the temporary elastic constants were computed after the stresses and stains were substituted into elastic mechanics equations. After iterative procedure, the convergent values of the elastic constants can be obtained. One numerical example and three experimental cases were proposed to show the applicability of this method. The convergent values of the five independent elastic constants can be obtained in no more than 10 iterative cycles. The results coming from numerical analysis method exhibited satisfactory outcome in accordance with those of generalized reduced gradient method. The merits of this method include convenient specimen preparation of the Brazilian test, simple iterative procedure, and readily available commercially numerical programs, so that this method can be easily popularized in research and engineering analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

Atmospheric teleconnection mechanisms of extratropical North Atlantic SST influence on Sahel rainfall

Extratropical North Atlantic cooling has been tied to droughts over the Sahel in both paleoclimate observations and modeling studies. This study, which uses an atmospheric general circulation model (GCM) coupled to a slab ocean model that simulates this connection, explores the hypothesis that the extratropical North Atlantic cooling causes the Sahel droughts via an atmospheric teleconnection mediated by tropospheric cooling. The drying is also produced in a regional climate model simulation of the Sahel when reductions in air temperature (and associated geopotential height and humidity changes) from the GCM simulation are imposed as the lateral boundary conditions. This latter simulation explicitly demonstrates the central role of tropospheric cooling in mediating the atmospheric teleconnection from extratropical North Atlantic cooling. Diagnostic analyses are applied to the GCM simulation to infer teleconnection mechanisms. An analysis of top of atmosphere radiative flux changes diagnosed with a radiative kernel technique shows that extratropical North Atlantic cooling is augmented by a positive low cloud feedback and advected downstream, cooling Europe and North Africa. The cooling over North Africa is further amplified by a reduced greenhouse effect from decreased atmospheric specific humidity. A moisture budget analysis shows that the direct moisture effect and monsoon weakening, both tied to the ambient cooling and resulting circulation changes, and feedbacks by vertical circulation and evaporation augment the rainfall reduction. Cooling over the Tropical North Atlantic in response to the prescribed extratropical cooling also augments the Sahel drying. Taken together, they suggest a thermodynamic pathway for the teleconnection. The teleconnection may also be applicable to understanding the North Atlantic influence on Sahel rainfall over the twentieth century.     

Reducing the impacts of flood-induced reservoir turbidity on a regional water supply system

This paper proposed an integrated simulation model to incorporate the impact of flood-induced reservoir turbidity into water supply. The integrated model includes a regional water allocation model and a one-dimensional settling model of cohesive particles based on Kynch’s theory. It simulates the settling of sediment flocculation in a turbid reservoir. The restrictions of water supply during floods is mimicked by simulating turbidity profiles for control points and then quantifying the associated treatment capability of raw water in the regional water allocation model for each time step. This framework can simulate shortages caused by flood-induced high turbidity as well as extended droughts, thus provide a basis for comprehensive evaluations of emergent and regular water supply facilities. A case study of evaluating different measures to mitigate the impact of turbid reservoir on water supply in northern Taiwan is presented to demonstrate the efficacy of the proposed approach.     

区域水安全评价指标体系构建与应用

水安全是耦合资源利用、环境保护、防灾等多维视角的复合概念。为提高水安全评价的系统完备性,避免各维度间概念重合,提升问题诊断的精确性,基于对水安全定义、内涵及评价维度的总结述评,构建了由数量充足性、水质符合性、可持续性、成本可承受性和防洪安全保证性5个评价维度构成的区域水安全评价指标体系,并结合专家群决策进行指标权重量化与数据标准化。该评价体系体现了资源安全中关于数量保障与可持续性保障的概念内涵,相比单纯利用资源禀赋指标评价水资源数量安全,更能科学辨析区域真实缺水原因;补充前人研究较少涉及的成本可承受性,保证了水安全内涵的系统完备性。以中国各省为例,结合聚类分析开展水安全评价的实例应用,评价结果较好地诊断了中国各区域主要水安全问题,符合中国现状,说明该评价体系具备较好的科学性与实用性。     

基于已知定向参数影像的光束法区域网平差

从自检校光束法区域网平差模型出发,建立了利用同一地区已知定向参数的影像解求新获取影像外方位元素并进行目标定位的数学模型。以此为基础,对来自某地区相隔两年的三期不同摄影比例尺航空影像两两组合地进行联合光束法区域网平差。结果表明,当两期影像比例尺相近时,所解求的新影像外方位元素和加密点坐标精度基本达到常规光束法区域网平差的精度;当两期影像比例尺不同时,利用已知定向参数的大比例尺影像解求出的小比例尺影像的外方位元素和加密点坐标可满足现行规范精度要求,利用已知定向参数的小比例尺影像去解求大比例尺影像的外方位元素和加密点坐标精度明显下降且不可用。本文的研究证实,就同一地区的多时相航摄影像而言,利用已知定向参数的影像进行新影像的定向方法是可行的。