RC框架结构薄弱层的层间位移可靠度水平考察   总被引：2，自引：0，他引：2  

吴波  李艺华 《地震工程与工程振动》2003,23(6):103-108

讨论了钢筋混凝土框架结构层间极限变形角的近似概率特性,考察了大震作用下20余幢钢筋混凝土框架结构薄弱层的层间位移可靠度水平,从而为直接基于位移可靠度的抗震设计中层间目标位移可靠度的确定提供了一定依据。  相似文献   

一个灵活的海洋——大气耦合环流模式   总被引：33，自引：13，他引：20  

Yu Yongqiang  Yu Rucong  Zhang Xuehong  Liu Hailong 《大气科学进展》2002,19(1):169-190

Based on the National Center for Atmospheric Research (NCAR) Climate System Model version 1(CSM-1), a Flexible coupled General Circulation Model version 0 (FGCM-0) is developed in this study through replacing CSM-1＇s oceanic component model with IAP L30T63 global oceanic general circulation model and some necessary modifications of the other component models. After the coupled model FGCM--0 is spun up for dozens of years, it has been run for 60 years without flux correction. The model does not only show the reasonable long-term mean climatology, but also reproduce a lot of features of the interannual variability of climate, e.g. the ENSO-like events in the tropical Pacific Ocean and the dipole mode pattern in the tropical Indian Ocean. Comparing FGCM-0 with the NCAR CSM-1, some common features are found, e.g. the overestimation of sea ice in the North Pacific and the simulated double ITCZ etc.The further analyses suggest that they may be attributed to errors in the atmospheric model.  相似文献   

Assessment of potential transport of pollutants into the Barents Sea via sea ice--an observational approach     

Korsnes R  Pavlova O  Godtliebsen F 《Marine pollution bulletin》2002,44(9):861-869

The present estimates of ice drift in the Arctic include utilization of satellite imagery data (special sensor microwave/imager) and a reconstruction of air pressure for the period 1899-1998. A significant part of the sea ice in the Arctic Ocean has its origin in the Kara Sea and melts in the Greenland and the Barents Sea (BS). Consequently there may be a particular risk of pollutants in the Kara Sea entering the food webs of the Greenland and BS. The ice export from the Kara Sea between 1988 and 1994 was about 208,000 km2 (154 km3) per year. The import of ice into the BS was during the same period 161,000 km2 (183 km3) per year while the ice drift through the Fram Strait into the Greenland Sea was 583,000 km2 (1859 km3) per year. Ice which formed adjacent to the Ob and Yenisey rivers in early January, drifted into the BS within two years (with a probability of about 50%.  相似文献   

无中导洞施工双连拱隧道的数值模拟分析     

赖金星  谢永利  李宁军 《水文地质工程地质》2006,33(3):68-71

针对双连拱隧道采用三导洞或中导洞超前施工方法施工工序多、临时支护量大的不足,以黄延高速公路羊泉沟隧道为例,提出在Ⅲ类围岩中采用无中导洞超前施工方法.基于弹塑性有限元方法对其施工过程进行分析,获得了施工各阶段围岩的应力、应变状态,以及初期支护和二次衬砌的受力状态.结果表明：在Ⅲ类围岩中连拱隧道采用无中导洞施工方法,围岩和支护结构处于安全状态.分析结果为羊泉沟隧道的顺利贯通提供了有效指导.  相似文献   

捷联惯导系统四元数转换误差分析     

毛克诚  孙付平 《测绘学院学报》2006,(4)

捷联惯性导航系统中,根据四元数与直余弦矩阵的关系可以得到3种转换矩阵。充分分析了这3种转换方案所产生的误差。并在恒定角速率下对3种不同转换矩阵中漂移误差、不对称误差和刻度误差进行评估,最后通过仿真验证了分析结果。  相似文献   

从大洋中脊反思大陆漂移说——兼论地球膨裂说     

白卉  闫玉英  沈文杰 《吉林地质》2007,26(2):71-74

本文通过讨论地幔对流的可能性以及大洋中脊的运动方式,证明了大陆漂移说对大陆漂移的源动力的解释仍存在漏洞,并提出大陆漂移源动力与地球膨裂的关系。对大陆漂移说具有补充性。  相似文献   

导航卫星原子钟频率漂移特性分析   总被引：2，自引：0，他引：2  

郭海荣  杨生  何海波 《全球定位系统》2007,32(6):5-10

介绍了原子钟频漂定义，总结了频率漂移率测试评定方法，比较分析了不同噪声情况下的频率漂移率估计方法，并用实验室真空状态铷钟的频率偏差数据和GPS卫星钟的精密星历数据进行了计算分析，表明铷钟都有明显频漂，GPSIIR铷钟的日漂移率在10^-15。量级，而铯钟频漂不是很明显。研究了频漂对原子钟时域稳定性影响规律，还利用模拟数据进行了计算分析。验证了方法的有效性．  相似文献   

塔克拉玛干沙漠石油公路沿线风沙活动的气候环境   总被引：5，自引：2，他引：3  

温向乐  韩致文 《中国沙漠》1998,18(1):77-80

塔克拉玛干沙漠石油公路沿线风沙活动是由塔木盆地内热能释放与冷空气入侵相互作用的结果。冷期,盆地内冷高压逆温作用较强,地面热能不足,使得风力和风沙活动强度弱;暖期,盆地内热源剧增,每当热能源饱和遇到冷空气入侵诱导,导致了强风及强风沙活动天气。可见,区内风沙活动及风成景观的塑造过程,主要是在暖干期进行的。  相似文献   

Paleobiogeography of Cretaceous larger Foraminifera of Pakistan and the Caribbean region and their bearing on continental drift     

A.A. Kureshy 《Cretaceous Research》1980,1(2):93-100

The Cretaceous larger Foraminifera of Pakistan are restricted to the Upper Cretaceous belonging to the species of Orbitoides Lepidorbitoides, Omphalocyclus, and Siderolites. The species of these genera are quite distinct in comparison to other assemblages of the Tethys region. None of these species are identical in the Mediterranean or Caribbean regions, with the exception of few concordant species of Orbitoides recorded in the deep-sea cores of Bahama Island. The paleo-ecological factor is the most important consideration in paleogeographic distribution of the Upper Cretaceous larger Foraminifera.  相似文献   

Post-breakup basaltic magmatism along the East Greenland Tertiary rifted margin     

Stefan Bernstein  Peter B Kelemen  Christian Tegner  Mark D Kurz  Jurek Blusztajn  C.Kent Brooks 《Earth and Planetary Science Letters》1998,160(3-4):845-862

Mafic and ultramafic intrusions in East Greenland adjacent to the offshore Greenland–Iceland ridge were emplaced 5–9 My after continental breakup at 55 Ma [1]. Rare earth element (REE) concentrations determined by secondary ion mass spectrometry are reported for cumulus clinopyroxene from these intrusions, and the data are used to estimate REE abundance in equilibrium melts using available partitioning data. Estimated equilibrium melts from intrusions have strongly fractionated REE patterns with Nd/Dy(N) in the range 2 to 5.6 and Yb/Dy(N) 0.55 to 0.92, similar to values for coeval basalts. These melts have markedly higher Nd/Dy(N) than earlier breakup related flood basalts. The moderately low Yb/Dy(N) for the post-breakup volcanism is indicative of residual garnet in the source, while their high Nd/Dy(N) ratios can best be explained by aggregating low degree melts from a light-REE-enriched garnet- and spinel-bearing mantle source. We also report He, Sr, and Nd isotopic data for the intrusions. The highest ³He/⁴He ratios (>10 R/R_a) are found in the samples whose REE data reflect the largest proportion of melts from a garnet-bearing source, and having Sr and Nd isotopic compositions identical with the radiogenic Sr and unradiogenic Nd isotope end of the Iceland compositional field. There is no indication of a MORB-type mantle in the source of the intrusions. We postulate that post-breakup volcanism along the East Greenland coastline reflects the increasing proximity of the mantle plume to the East Greenland continental margin. The low degree of melting at high mean pressure inferred for the parental melts for the intrusions may reflect re-thickening of the lithosphere, which in turn was caused by the vigorous volcanism during breakup, with accompanying depletion of upper mantle and underplating of the crust at the continental margin.  相似文献