On the field-aligned currents pattern formation in the magnetosphere     

P. Nenovski  D. Danov  A. Bochev   《Journal of Atmospheric and Solar》2003,65(16-18):1369-1383

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Estimation of fundamental periods of shear‐wall dominant building structures     

Can Balkaya  Erol Kalkan 《地震工程与结构动力学》2003,32(7):985-998

Shear‐wall dominant multistorey reinforced concrete structures, constructed by using a special tunnel form technique are commonly built in countries facing a substantial seismic risk, such as Chile, Japan, Italy and Turkey. In spite of their high resistance to earthquake excitations, current seismic code provisions including the Uniform Building Code (International Conference of Building Officials, Whittier, CA, 1997) and the Turkish Seismic Code (Specification for Structures to be Built in Disaster Areas, Ankara, Turkey, 1998) present limited information for their design criteria. In this study, consistency of equations in those seismic codes related to their dynamic properties are investigated and it is observed that the given empirical equations for prediction of fundamental periods of this specific type of structures yield inaccurate results. For that reason, a total of 80 different building configurations were analysed by using three‐dimensional finite‐element modelling and a set of new empirical equations was proposed. The results of the analyses demonstrate that given formulas including new parameters provide accurate predictions for the broad range of different architectural configurations, roof heights and shear‐wall distributions, and may be used as an efficient tool for the implicit design of these structures. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Evaluating foundation mass,damping and stiffness by the least‐squares method     

S. H. Ju 《地震工程与结构动力学》2003,32(9):1431-1442

This paper discusses how to use the three‐dimensional (3D) time‐domain finite‐element method incorporating the least‐squares method to calculate the equivalent foundation mass, damping and stiffness matrices. Numerical simulations indicate that the accuracy of these equivalent matrices is acceptable when the applied harmonic force of 1+sine is used. Moreover, the accuracy of the least‐squares method using the 1+sine force is not sensitive to the first time step for inclusion of data. Since the finite‐element method can model problems flexibly, the equivalent mass, damping and stiffness matrices of very complicated soil profiles and foundations can be established without difficulty using this least‐squares method. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

济阳坳陷稀土元素特征及其在物源对比中的应用   总被引：6，自引：1，他引：6  

陈庆春  吴智平李伟 《地质论评》2003,49(6):622-629

物源是控制沉积物中REE组成最主要的因素，济阳坳陷区岩石稀土元素特征表明：①济阳坳陷古生界与华北地台其他地区同时代地层岩石的REE分布特征具有极大的相似性，这体现了晚古生代济阳坳陷区所处的整个华北地台区为一稳定的克拉通沉积盆地，地层横向分布稳定，具有一致的物源和构造背景；②济阳坳陷古生界为中生界的物源，反映了济阳坳陷区由古生代稳定地台型沉积到中生代山间盆地沉积的转变，中生代洼陷区的沉积主要来自对附近凸起区古生代地层的剥蚀；③新生界样品与中生界样品的REE分布模式具有很大的相似性，从一个侧面反映了济阳坳陷中生代与新生代的构造格局的转变，中生代接受沉积的部分洼陷区至古近纪成为供给物源的凸起区。  相似文献   

Laser Ablation ICP-MS Analysis of Geological Materials Prepared as Lithium Borate Glasses   总被引：9，自引：0，他引：9  

Stephen M. Eggins 《Geostandards and Geoanalytical Research》2003,27(2):147-162

A simple, rapid and precise method is described for determining trace elements by laser ablation (LA)-ICP-MS analysis in bulk geological materials that have been prepared as lithium borate glasses following standard procedures for XRF analysis. This approach reliably achieves complete sample digestion and provides for complementary XRF and LA-ICP-MS analysis of a full suite of major and trace elements from a single sample preparation. Highly precise analysis is enabled by rastering an ArF excimer laser (λ= 193nm) across fused samples to deliver a constant sample yield to the mass spectrometer without inter-element fractionation effects during each analysis. Capabilities of the method are demonstrated by determination of twenty five trace elements (Sc, Ti, V, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, REE, Hf, Ta, Pb, Th and U) in a diverse range of geological reference materials that includes peridotites, basalts, granites, metamorphic rocks and sediments. More than 90% of determinations are indistinguishable from published reference values at the 95% confidence level. Systematic bias greater than 5% is observed for only a handful of elements (Zr, Nb and U) and may be attributed in part to inaccurate calibration values used for the NIST SRM 612 glass in the case of Zr and Nb. Detection limits for several elements, most notably La, are compromised at ultra-trace levels by impurities in the lithium borate flux but can be corrected for by subtracting appropriate procedural blanks. Reliable Pb analysis has proved problematic due to variable degrees of contamination introduced during sample polishing prior to analysis and from Pt-crucibles previously used to fuse Pb-rich samples. Scope exists for extending the method to include internal standard element/isotope spiking, particularly where integrated XRF analysis is not available to characterise major and trace elements in the fused lithium borate glasses prior to LA-ICP-MS analysis.  相似文献   

A Reappraisal of Rb, Y, Zr, Pb and Th Values in Geochemical Reference Material BHVO-1     

William J. Chazey III  Clive R. Neal  Jinesh C. Jain  William S. Kinman 《Geostandards and Geoanalytical Research》2003,27(2):181-192

The geochemical reference material BHVO-1 was analysed by a variety of techniques over a six year period. These techniques included inductively coupled plasma-mass spectrometry and atomic emission spectroscopy (ICP-MS and ICP-AES, respectively), laser ablation ICP-MS and spark source mass spectroscopy. Inconsistencies between the published consensus values reported by Gladney and Roelandts (1988, Geostandards Newsletter) and the results of our study are noted for Rb, Y, Zr, Pb and Th. The values reported here for Rb, Y, Zr and Pb are generally lower, while Th is higher than the consensus value. This is not an analytical artefact unique to the University of Notre Dame ICP-MS facility, as most of the BHVO-1 analyses reported over the last ten to twenty years are in agreement with our results. We propose new consensus values for each of these elements as follows: Rb = 9.3 ± 0.2 μg g-1 (compared to 11 ± 2 μg g-1), Y = 24.4 ± 1.3 μg g-1 (compared to 27.6 ± 1.7 μg g-1), Zr = 172 ± 10 μg g-1 (compared to 179 ± 21 μg g-1), Pb = 2.2 ± 0.2 μg g-1 (compared to 2.6 ± 0.9 μg g-1) and Th = 1.22 ± 0.02 μg g-1 (compared to 1.08 ± 0.15 μg g-1).  相似文献   

岩溶地区桩基的有限元分析     

艾凯  王静 《岩土力学》2003,(Z1)

岩溶地区长桩存在着遇洞率的问题。为了研究岩溶地区桩的受力特点,采用有限元法模拟岩溶地区桩基的工作方式,分析了岩层厚度对桩的影响以及桩的受力状态,并研究了去桩的可能性。计算结果表明:岩层厚度对桩的影响较大,岩层的位置对桩的应力不产生影响,仅对桩的位移产生影响。  相似文献   

饱水黄土隧道变形规律研究   总被引：7，自引：0，他引：7  

乔春生  管振祥  滕文彦 《岩土力学》2003,(Z2)

新松树湾隧道位于饱和的砂粘土中,土体的稳定性极差,施工难度较大。为此,在隧道施工期间,通过土工试验、隧道收敛和围岩内部位移的现场监测、隧道变形的三维有限元仿真计算等手段,对该隧道的变形规律进行了系统研究,获得了大量试验数据。研究成果对隧道的施工组织和支护参数的确定起到了重要作用,为此类隧道的施工积累了经验。  相似文献   

富水水库中微生物成因的显微针铁矿及其对微量元素的富集   总被引：3，自引：0，他引：3       下载免费PDF全文

车遥  胡宝林  夏林  孙振亚  王利忠 《地球学报》2003,24(2):161-166

通过对湖北省富水水库坝基渗漏水及其析出物的研究，探讨了现代沉积环境（水库）中显微铁矿物形成的机理及微生物在铁的生物矿化中的作用和意义。对析出物中微量元素的富集特征也进行了初步研究。用化学分析方法测试出坝基渗漏水中阳离子以Ca^2 、Mg^2 、K^ 、Na^ 为主，Fe^2 和Fe^3 含量极少，阴离子以HCO3^-为主。析出物的化学成分以铁的氧化物为主。采用X射线衍射、差热分析、红外光谱和穆斯堡尔谱，以及透射电镜和扫描电镜等测试手段，分析研究了析出物的物相和形貌特征。析出物的主要矿物相为针铁矿、石英、伊利石、蒙脱石和微量方解石，呈弱结晶状态。由析出物中显微针铁矿特殊的形貌特征及其特征的穆斯堡尔谱图推测出富水水库沉积环境中显微针铁矿是由铁细菌形成。ICP－MS测试测试结果表明，析出物中不仅富集了铁，还富集了Yb、Pb、Dy、Zn、Co、Be、Eu、Sm和Tb等微量元素。微量元素的富集是微生物与显微针铁矿共同作用的结果。  相似文献   

黄河上游河南县地面大气冰核观测分析   总被引：7，自引：2，他引：7       下载免费PDF全文

李淑日黄庚  胡志晋 《应用气象学报》2003,14(Z1):41-48

用Bigg型混合云室对2001年8月黄河上游青海省河南县的地面大气冰核浓度进行了观测,分析发现(1)青海省河南县冰核浓度低于北京20世纪90年代的测值,但高于大连、西安和兰州(20世纪60年代)等地的测值,同时也高于黄河上游的玛曲(2000年)、西宁(1989年)两地的测值,高温核尤其偏高.(2)降水时大气冰核浓度减少,降水的冲刷可能是其主要原因.(3)当地冰核浓度和气压成正相关.(4)大气冰核浓度受风向的影响,无风时测值较小,偏东风时测值较大,高温核浓度增加明显.  相似文献