疏散星团NGC6530天区的恒星自行和成员概率     

温文  赵君亮陈力 《中国科学院上海天文台年刊》2005,(1):79-94

利用上海天文台的照相底片资料,确定了疏散星团NGC6530天区364颗恒星的自行和成员概率,并对有关自行测定的方法、结果和精度等问题作了较为详细的介绍和讨论。使用的底片历元差为87年,全部恒星自行中误差的均方根值为1．09mas/a。  相似文献   

Predicting ground-motion variations at the Turkey-flat test site,California     

J. Zahradník  J. Jech  V. Barták 《Pure and Applied Geophysics》1991,137(1-2):63-84

Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time.  相似文献   

Crystal-Melt Separation and the Development of Isotopic Heterogeneities in Hybrid Magmas     

Beard  James S. 《Journal of Petrology》2008,49(5):1027-1041

If a magma is a hybrid of two (or more) isotopically distinctend-members, at least one of which is partially crystalline,separation of melt and crystals after hybridization will leadto the development of isotopic heterogeneities in the magmaas long as some of the pre-existing crystalline material (antecrysts)retains any of its original isotopic composition. This holdstrue whether the hybridization event is magma mixing as traditionallyconstrued, bulk assimilation, or melt assimilation. Once a magma-scaleisotopic heterogeneity is formed by crystal–melt separation,it is essentially permanent, persisting regardless of subsequentcrystallization, mixing, or equilibration events. The magnitudeof the isotopic variability resulting from crystal–meltseparation can be as large as that resulting from differentialcontamination, multiple isotopically distinct sources, or insitu isotopic evolution. In one model, a redistribution of one-thirdof the antecryst cargo yielded a crystal-enriched sample with⁸⁷Sr/⁸⁶Sr of 0·7058, whereas the complementary crystal-poorsample has ⁸⁷Sr/⁸⁶Sr of 0·7068. In other models, crystal-richsamples are enriched in radiogenic Sr. Isotopic heterogeneitiescan be either continuous (controlled by the modal distributionof crystals and melt) or discontinuous (when there is completeseparation of crystals and liquid). The first case may be exemplifiedby some isotopically zoned large-volume rhyolites, formed bythe eruptive inversion of a modally zoned magma chamber. Inthe latter case, the isotopic composition of any (for example)interstitial liquid will be distinct from the isotopic compositionof the bulk crystal fraction. The separation of such an interstitialliquid may explain the presence of isotopically distinct late-stageaplites in plutons. Crystal–melt separation provides anadditional option for the interpretation of isotopically zonedor heterogeneous magmas. This option is particularly attractivefor systems whose chemical variation is otherwise explicableby fractionation-dominated processes. Non-isotopic chemicalheterogeneities can also develop in this fashion. KEY WORDS: isotopic heterogeneity; zoning; hybrid magma; crystal separation; Sr isotopes; aplite; rhyolite  相似文献   

Crystal chemical significance of chemical zoning in dissakisite-(Ce)     

Mihoko Hoshino  Mitsuyoshi Kimata  Norimasa Nishida  Masahiro Shimizu 《Physics and Chemistry of Minerals》2008,35(2):59-70

Dissakisites from Trimouns dolomite mine, France, have two kinds of single crystals: chemical-zoned and homogeneous types. Back-scattered electron microprobe (BSE) images of these dissakisites reveal both Ca–Al rich dark zones and Fe-ΣREE rich bright zones. Crystal structures of three dark and two bright zones in a chemical-zoned dissakisite and of a homogeneous zone in unzoned dissakisite were refined to individual R indices (about 3.0–5.0%) based on 1,400 observed [|F ₀| > 4σF ₀] reflections measured with MoKα X-radiation using the single crystal diffractometer. The differences in brightness between their BSE images arise from those in coupled substitutions of the elements occupying A2 and M3 sites. The main reason for these differences is that ten-coordinated A2 polyhedra and M3 octahedra are directly linked through their shared edge, which creates a great potential for making this coupled substitution. This zoning indicates that formation of the whole zoned crystal, where each zone could be grown steadily with its crystallographic axes mutually parallel to each other, may be identified as autoepitaxy.  相似文献   

Influence of Structural Non-Stationarity of Surface Roughness on Morphological Characterization and Mechanical Deformation of Rock Joints   总被引：2，自引：2，他引：0  

N. Fardin 《Rock Mechanics and Rock Engineering》2008,41(2):267-297

Summary Structural non-stationarity of surface roughness affects accurate morphological characterization as well as mechanical behaviour of rock joints at the laboratory scale using samples with a size below the stationarity threshold. In this paper, the effect of structural non-stationarity of surface roughness is investigated by studying the scale dependence of surface roughness and mechanical behaviour of rock joints. The results show that the structural non-stationarity mainly affects the accurate characterization of the surface roughness of the fracture samples. It also controls the amount and location of the contact areas during shear tests, which in turn affects the mechanical properties and asperity degradation of the samples. It is concluded that for accurate determination of the morphological and mechanical properties of rock joints at laboratory and field scales, samples with size equal to or larger than the stationarity threshold are required. Author’s address: Nader Fardin, Rock Mechanics Group, Department of Mining Engineering, Faculty of Engineering, University of Tehran, P.O. Box: 11365/4563, Tehran, Iran  相似文献   

Ground motion estimation during the Kashmir earthquake of 8th October 2005   总被引：2，自引：1，他引：1  

S. T. G. Raghukanth 《Natural Hazards》2008,46(1):1-13

In this article, analytical methods have been used to estimate ground motion during the 8 October 2005, Kashmir earthquake. Peak ground acceleration (PGA) values at several stations in the epicentral region have been estimated by empirical analytical source mechanism models. As an alternate analysis, PGA estimates have also been obtained using the stochastic finite fault seismological model. The estimated PGAs are compared with that obtained from damage values. A PGA contour map in the near-source region is provided. It is found that very near to the epicenter, PGA would have reached more than 1 g. It is demonstrated that empirical analytical models can be effectively used to estimate ground motion due to rupture of active faults.  相似文献   

流域水文模型参数识别的现代优化方法研究进展   总被引：1，自引：1，他引：0  

武震  张世强  张小文 《冰川冻土》2008,30(1):64-71

水文参数优化是水文模型发展中的一个重要部分,针对水循环过程模拟中的流域水文模型参数识别的复杂优化问题,回顾了水文模型优化算法的发展历程,对国内外水文模型参数识别算法的最新进展进行了阐述.介绍了模拟退火算法、遗传算法、SCE-UA、粒子群算法等常用算法的参数设定及一般流程,并对编码遗传算法、单纯形混合加速遗传算法和运用融合技术的几种遗传算法以及其它几种常用算法在新安江模型中的优化结果进行了比较,认为混合加速遗传算法是一种较好的方法.在系统研究现代优化算法与传统优化算法的基础上,建立各种优化算法的融合技术和法则可能是进一步提高参数优化算法性能的方向.  相似文献   

中国-俄罗斯原油管道工程(漠河-大庆段)冻土工程地质考察与研究进展   总被引：4，自引：2，他引：2  

李国玉  金会军  盛煜  张建明  俞祁浩  齐吉琳  温智  吕兰芝  童长江  郭东信  王绍令  魏智  杨思忠  吉延俊  于少鹏  何瑞霞  常晓丽  郝加前  陈友昌  吴伟  翟镇远  赵意民 《冰川冻土》2008,30(1):170-175

在2005-2007年期间,先后3次对中国-俄罗斯原油管道漠河-大庆段沿线的冻土工程地质条件等进行科学考察,开展了冻土工程地质条件及其在气候变化和人类活动作用下的评价和预测研究.考察研究结果表明:管道沿线多年冻土在各类融区、季节冻土和水系等分隔作用下呈片状或岛状分布,沿线岛状、稀疏岛状及零星岛状占多年冻土区段的40%左右;管道沿线多年冻土随着气候的转暖和人类活动的影响不断退化.地形地貌单元、植被分布、地表水分条件的变化等局部因素对多年冻土的分布和地下冰的赋存产生重要的影响,管道沿线大约分布有50 km左右的沼泽湿地,其表层为腐殖质土及泥炭层,泥炭层下面分布着含土冰层或地下冰,是管道沿线最差的冻土工程地质地段;由于中俄原油管道沿线水系发育多,冻胀丘、冰椎和冰幔等不良冻土现象广泛分布.科学考察的成果为管道沿线冻土工程地质条件评价和预测、管道的稳定性影响分析以及后期的长期检测系统设置等研究奠定坚实的基础,进一步为即将开工的中俄原油管道漠河-大庆段工程的设计、施工提供科学依据.  相似文献   

江苏潮滩沉积物激光粒度仪与移液管-筛析分析结果的对比     

仝长亮  高抒 《沉积学报》2008,26(1):46-53

激光粒度仪的广泛应用带来了与历史数据的对比问题,因此需要建立激光粒度仪与早期分析结果之间的关系。根据江苏海岸潮滩沉积物样品的激光粒度仪和移液管-筛析法分析,对粒度参数、粒度组分等进行了对比,对两种方法的差异进行了分析。结果表明,对于江苏潮滩沉积物粒度参数中平均粒径的激光粒度仪与移液管-筛析分析结果之间有良好的线性关系;筛分法测得的粗颗粒物质较激光法偏少,而移液管法法测得的细颗粒物质较激光法偏多;将样品分类之后再进行两种方法所获粒度参数的回归分析,相关性得以提高,说明不同粒度组成的沉积物对分析结果的对比有不同的影响。两种方法之间的换算关系不仅与研究区域有关,而且与沉积物本身的粒度组成有关。  相似文献   

软硬互层金刚石复合片钻头在地浸砂岩型铀矿中的研究及应用          下载免费PDF全文

要二仓  邢预恩  杨爱军 《探矿工程》2008,35(1):68-70

针对近年在巴音戈壁盆地及鄂尔多斯盆地钻探所遇到的复杂地质情况,研究试验了PDC钻头,在地浸砂岩铀矿钻探生产中取得了良好的效果,并制定总结了相应的钻进参数.  相似文献