罗圈里撞击坑铂族元素异常及粗铂矿的发现及其意义   总被引：5，自引：0，他引：5  

覃功炯  卢登蓉等 《地学前缘》2001,8(2):333-338

对 1998年 7月发现的辽宁岫岩县苏子沟镇罗圈里直径 1.8km的撞击坑构造作了一系列地质、地球化学测试工作。从坑内出露的基岩 (下元古界辽河群里尔峪组变质砂岩 )与充填碎屑物质界面上取样 ,经XRD定性分析显示有自然铂、锇铱矿、自然铑、自然铱的存在。进一步对这一类样品作等离子质谱分析 (ICP MS) ,则发现有PGE异常。特别是Pt,Pd ,Ru甚至高于原始地幔的丰度值。进一步淘选坑里重砂样品则发现数颗粗铂矿物。已作电子探针分析表明PGE质量分数 :Pt为 85 .30 % 98.6 8% ,Pd为 0 .45 % 0 .87% ,Rh为 0 .5 6 % 0 .74% ,Os为 0 .6 6 % 1.31% ,Ir为 1.72 % 2 .43% ,Ru为 0 .16 % 0 .31% ,此外Ni为 0 .0 0 % 0 .5 0 % ,Fe为 4.98% 5 .42 %。笔者认为这种PGE元素异常和粗铂矿的发现是陨石及其撞击作用的重要依据之一。  相似文献   

Pounding of structures modelled as non‐linear impacts of two oscillators     

K. T. Chau  X. X. Wei 《地震工程与结构动力学》2001,30(5):633-651

A new formulation is proposed to model pounding between two adjacent structures, with natural periods T₁ and T₂ and damping ratios ζ₁ and ζ₂ under harmonic earthquake excitation, as non‐linear Hertzian impact between two single‐degree‐of‐freedom oscillators. For the case of rigid impacts, a special case of our analytical solution has been given by Davis (‘Pounding of buildings modelled by an impact oscillator’ Earthquake Engineering and Structural Dynamics, 1992; 21 :253–274) for an oscillator pounding on a stationary barrier. Our analytical predictions for rigid impacts agree qualitatively with our numerical simulations for non‐rigid impacts. When the difference in natural periods between the two oscillators increases, the impact velocity also increases drastically. The impact velocity spectrum is, however, relatively insensitive to the standoff distance. The maximum relative impact velocity of the coupled system can occur at an excitation period T_n^* which is either between those of the two oscillators or less than both of them, depending on the ratios T₁/T₂ and ζ₁/ζ₂. Although the pounding force between two oscillators has been primarily modelled by the Hertz contact law, parametric studies show that the maximum relative impact velocity is not very sensitive to changes in the contact parameters. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

金刚石碎岩工具胎体材料添加稀土元素的试验研究   总被引：5，自引：1，他引：5       下载免费PDF全文

汤凤林杨凯华  邹庆化段隆臣　胡国荣 《探矿工程》2001,(1):45-48

对胎体材料中添加稀土元素问题进行了试验研究。对添加稀土和未加稀土的胎体性能进行测试，结果表明，添加稀土比未加稀土的胎体材料的抗弯强度、硬度和冲击韧性均有所提高，其中抗弯强度提高了10％－62％，冲击韧性提高了5％。胎体中添加稀土对提高胎体和金刚石碎岩工具的技术经济指标具有重要作用,并且为在胎体材料中实现以Fe代Co创造了有利条件。  相似文献   

气候变化对京津唐地区水资源及供需平衡的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

王建生  张世法 《水科学进展》1996,7(1):26-36

根据大气环流模型(GCMs)输出的未来气候变化情景,结合历史资料的诊断分析,应用建立的流域水文模型及水资源利用综合评价模型,研究了气候变化对京津唐地区水资源数量和时空变化的影响。在地区未来经济发展及部门用水量预测的基础上,分析了气候变化对供水、需水和部门缺水的影响以及经济损失。  相似文献   

THE IMPACT OF NOAA SATELLITE SOUNDING DATA ON THE SYSTEMATIC FORECAST ERROR OF B-MODEL          下载免费PDF全文

Wang Zonghao  Mao Jianping  Huang Jihong  Arnold Gruber  Albert Thomasell  Tan Sun Chen 《Acta Meteorologica Sinica》1992,6(4):421-432

This paper is to examine the impact of satellite data on the systematic error of operational B-model in China.Em-phasis is put on the study of the impact of satellite sounding data on forecasts of the sea level pressure field and 500 hPaheight.The major findings are as follows.(1)The B-model usually underforecasts the strength of features in the sea level pressure(SLP)field,i.e.pressuresare too low near high pressure systems and too high near low pressure systems.(2)The nature of the systematic errors found in the 500 hPa height forecasts is not as clear cut as that of the SLPforecasts,but most often the same type of pattern is seen,i.e.,the heights in troughs are not low enough and those inridges are not high enough.(3)The use of satellite data in the B-model analysis/forecast system is found to have an impact upon the model'sforecast of SLP and 500 hPa height.Systematic errors in the vicinity of surface lows/500 hPa troughs over the oceansare usually found to be significantly reduced.A less conclusive mix of positive and negative impacts was found for allother types of features.  相似文献   

埃尔塔宁小行星质量的下限估计     

苏晠  张延安 《紫金山天文台台刊》1999,18(1):26-31

埃尔塔宁小行星是一颗２１５ 万年前在南太平洋撞击地球的小行星,它也是目前唯一的深海区与地球碰撞的小行星。根据埃尔塔宁号和Ｐｏｌａｒｓｔｅｒｎ 号海洋调查船在陨击海区勘查的小行星残骸分布密度,我们估计埃尔塔宁小行星质量为２ ．３ ×１０１３ｇ ,对应于它的直径为０ ．２３ 公里。这比Ｋｙｔｅ 等人（１９８８） 估计的质量小了１０ 倍,然而它更接近埃尔塔宁小行星撞击事件的实际情况,可以作为埃尔塔宁小行星质量下限和半径下限更合理的估计值。  相似文献   

环境影响评价中的效益—费用分析方法     

刁瑞田  邓新民 《成都信息工程学院学报》1993,(1)

效益-费用分析方法是环境影响评价中一种重要的方法。本文介绍了环境影响评价中的效益-费用分析方法的理论、程序及定量评价技术,概述了环境影响评价中效益-费用分析方法的理论及应用进展,并针对其存在问题,进行了探讨。  相似文献   

Implementation of configuration dependent stiffness proportional damping for the dynamics of rigid multi-block systems     

Yun?Byeong?Chae  Jae?Kwan?KimEmail author 《地震工程与工程振动(英文版)》2003,2(1):87-97

The distinct element method (DEM) has been used successfully for the dynamic analysis of rigid block systems. One of many difficulties associated with DEM is modeling of damping. In this paper, new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid multi-block systems. The stiffness proportional damping is constructed for the prescribed damping ratio, based on the non-zero fundamental frequency effective during the time interval while the boundary conditions remain essentially constant. At this time interval, the fundamental frequency can be estimated without complete eigenvalue analysis. The damping coefficients will vary while the damping ratio remains the same throughout the entire analysis. A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases. These procedures were implemented in the development of the distinct element method for the dynamic analyses of piled multi-block systems. The analysis results for the single-block and two-block systems were in a good agreement with the analytic predictions. Applications to the seismic analyses of piled fourblock systems revealed that the new procedures can make a significant difference and may lead to much-improved results.  相似文献   

Natural and artificial connections between atoll islets in the pacific,their process and environmental impact     

Russell Howorth 《中国海洋大学学报(英文版)》2003,2(2):195-200

Three types of natural connection between atoll islets are described. Causeway, as an artificial way of connecting islets, makes a connection to be completed in a few months. In this case shore adjustment becomes more vigorous than that in natural conditions, resulting in lagoon shore erosion. A causeway without short bridges or culverts should be built close to the lagoon shore to reduce lagoon shore erosion. A causeway-crossing channel assemblage is the worst type among all of the connection engineering constructions because the crossing channel traps sediment and further transports it out of the channel, resulting in long period coastal erosion. Reforming Nippon Causeway in Tarawa Atoll, Kiribati by simple means will stop sand loss, reduce shore erosion and greatly upgrade its stability.  相似文献   

EROD activity, serum SDH and PAH biliary metabolites in sand flathead (Platycephalus bassensis) collected in Port Phillip Bay, Australia     

Gagnon MM  Holdway DA 《Marine pollution bulletin》2002,44(3):230-237

In order to evaluate the health status of fish inhabiting Port Phillip Bay, Australia, southern sand flathead (Platycephalus hassensis, N = 133) were collected at six stations throughout the Bay. Fish had a similar serum sorbitol dehydrogenase (SDH) activity level (p = 0.12), indicating that they were not experiencing hepatocellular injuries. Ethoxyresorufin-O-deethylase (EROD) activity was generally lower in the non-urbanized and non-industrialized southern part of the Bay. The highest EROD activity was observed in Hobson Bay, the closest station from Melbourne city. Naphthalene-type biliary metabolites were also highest in Hobson Bay with intermediate levels found in Corio Bay where refineries are present. An opposite trend was observed with the pyrene-type bile metabolites, the highest levels being observed in Corio Bay while intermediate levels were found in Hobson Bay. The ratio of naphthalene-type to benzo(a)pyrene (B(a)P)-type metabolites indicate that relatively to other sites sampled in Port Phillip Bay, Corio Bay is subjected to enriched petroleum hydrocarbons of pyrolytic origin. Temporal trends indicate that the availability of xenobiotics to fish remained unchanged over the 1990s.  相似文献